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Home | Alpha Telephone | Domain Names | Web Hosting | Get Traffic | xrEvidence | xrSoccer United States Patent
Telephone line communications control system The present invention is a telecommunications control system for accepting a plurality of multi-purpose stations for use as attendant stations in an attendant service complex to service calls directed to the system from originating stations. This system comprises a first plurality of connection controllers. Each connection controller in this first plurality of connection controllers provides for cooperating with a respective one of a plurality of multi-purpose stations in defining opposite ends of a call connection path. Each of these connection controllers has controllable switching means for opening the call connection path and releasing the respective multi-purpose station. The system provides for security against use of any of the multi-purpose stations within the attendant service complex by an unauthorized person. This system further includes a second plurality of connection controllers. Each connection controller is this second plurality of connection controllers provides for cooperating with a respective one of a pluraity of originating stations in defining opposite ends of a call connection path. This system further includes controllable inter-connection arranged between the first and second plurality of connection controllers, and includes a system for controlling the inter-connection system such that incoming calls from originating stations are extended to multi-purpose stations that have been accepted as attendant stations.
Attorney, Agent or Firm: CROSS-REFERENCE TO RELATED APPLICATIONS This is a continuation of application Ser. No. 07/106,726, filed 10/5/87 now abandoned. We claim: 1. A telecommunications control system for accepting a plurality of multi-purpose stations for use as attendant stations in an attendant service complex to service calls directed to the system from originating stations, the system comprising: a first plurality of station connection controllers, each station connection controller in the first plurality for cooperating with a respective one of a plurality of multi-purpose stations in defining opposite ends of a call connection path, and each such station connection controller having controllable switching means for opening the call connection path and releasing the respective multi-purpose station; means for providing security against use of any of the multi-purpose stations within the attendant service complex by an unauthorized person, the means for providing security including means for controlling the switching means to open the call connection path and release the multi-purpose station; a second plurality of station connection controllers, each station connection controller in the second plurality for cooperating with a respective one of a plurality of originating stations in defining opposite ends of a call connection path; controllable inter-connection means arranged between the first and second plurality of station connection controllers; and means for controlling the inter-connection means such that incoming calls from originating stations are extended to multi-purpose stations that have been accepted as attendant stations. 2. A system according to claim 1, wherein the means for providing security includes means for receiving a security-clearance signal via the call connection path to a multi-purpose station. 3. A system according to claim 2, wherein the means for providing security includes timer means for defining a timing interval to allow for receiving the security-clearance signal. 4. A system according to claim 3, wherein the means for receiving the security-clearance signal includes means for converting an in-band signal to a logic signal; wherein the timer means produces a logic signal to define the timing interval end; wherein the means for controlling the switching means to release a multi-purpose station comprises logic circuit means. 5. A system according to claim 1, wherein the second plurality of station connection controllers are connected to incoming lines. 6. A system according to claim 5, wherein each incoming line is a ground start line. 7. A system according to claim 5, wherein the incoming lines are connected to the public switched network. 8. A system according to claim 7, wherein each incoming line is a ground start line. 9. A system according to claim 7, wherein each incoming line has a toll-free telephone number. 10. A system according to claim 9, wherein each incoming line is a ground start line. 11. A system according to claim 1, and further comprising means for originating calls from the system to the multi-purpose stations. 12. A system according to claim 11, wherein the means for originating calls from the system comprises means for generating a sequence of signals to identify a multi-purpose station. 13. A system according to claim 12, wherein the first plurality of station connection controllers are connected to outgoing lines connected to the public switched network, whereby the multi-purpose stations can be located in homes. 14. A system according to claim 12, wherein the means for originating calls from the system includes means for automatically redialing, whereby an interrupted call to a multi-purpose station can be re-established. 15. A system according to claim 12, wherein the means for originating calls from the system includes means operating automatically in an operation to replace an inactivated multi-purpose station, whereby an auxiliary attendant can be substituted to provide service. 16. A system according to claim 1, wherein the controllable inter-connection means comprises a plurality of interconnecting switch means, and wherein the means for controlling the inter-connection means comprises means for controlling the interconnecting switch means such that a plurality of incoming calls are extended to the same multi-purpose station during an interval throughout which the multi-purpose station remains connected as an attendant station. 17. A system according to claim 16, and further comprising means for originating calls from the system to the multi-purpose stations. 18. A system according to claim 17, wherein the means for originating calls from the system comprises means for generating number-representing signals in a sequence to identify a multi-purpose station. 19. A system according to claim 18, wherein the first plurality of station connection controllers are connected to outgoing lines connected to the public switched network, whereby the multi-purpose stations can be located in homes. 20. A system according to claim 18, wherein the means for originating calls from the system includes means for automatically redialing, whereby an interrupted call to a multi-purpose station can be re-established. 21. A system according to claim 18, wherein the means for originating calls from the system includes means operating automatically in an operation to replace an inactivated multi-purpose station, whereby an auxiliary attendant can be substituted to provide service. 22. A system according to claim 16, and further comprising in-band signal responsive means for controlling the second plurality of station connection controllers such that an attendant at a multi-purpose station can disconnect an incoming call yet remain on line to be ready to have another incoming call extended to the on-line multi-purpose station. 23. A system according to claim 1, wherein the system is operable in traffic-volume dependent modes, and includes means operative during one such mode to release a multi-purpose station, then respond to a request to establish a call connection path for an incoming call by originating a call to, and re-establishing the previously released multi-purpose station as an attendant station, and then substantially simultaneously complying with the request and extending the incoming call to the re-established attendant station. 24. A system according to claim 23, wherein each of the second plurality of station connection controllers includes a ringing signal detection circuit for detecting such a request to establish a call connection path for an incoming call. 25. A system according to claim 24, wherein the ringing signal detection circuit produces a signal used to initiate a sequence of operations that are carried out while the ringing signal is present, and that thereby are transparent to the person placing the incoming call, by which an outgoing call is completed to a multi-purpose station and thereafter the incoming call is answered. 26. A system according to claim 1, wherein the first plurality of station connection controllers are connected to outgoing lines connected to the public switched network, whereby the multi-purpose stations can be located in homes. 27. A system according to claim 1, and further comprising means for playing a pre-recorded message to prompt an authorized person to enter a security-clearance signal. 28. A system according to claim 1, wherein the controllable inter-connection means comprises a plurality of interconnecting switch means, and wherein the means for controlling the inter-connection means comprises means for controlling the interconnecting switch means such that a plurality of incoming calls are extended to the same multi-purpose station during an interval throughout which the multi-purpose station remains connected as an attendant station, and further comprising means for playing a pre-recorded message after the last of the plurality of incoming calls and substantially immediately thereafter releasing the multi-purpose station. 29. A telecommunications control system for networking a plurality of multi-purpose telephone stations for use as attendant stations in an attendant service complex to service calls directed to the system from originating stations, the system comprising: a first plurality of station connection controllers, each station connection controller in the first plurality for cooperating with a respective one of a plurality of multi-purpose stations in defining opposite ends of a call connection path; a second plurality of station connection controllers, each station connection controller in the second plurality for cooperating with a respective one of a plurality of originating stations in defining opposite ends of a call connection path; controllable inter-connection means arranged between the first and second plurality of station connection controllers; and means for controlling the inter-connection means such that incoming calls from originating stations are extended to multi-purpose stations that have been networked for use as attendant stations, and wherein the means for controlling the inter-connection means includes means for causing a plurality of incoming calls to be extended to the same multi-purpose station during an interval throughout which the multi-purpose station remains networked as an attendant station. 30. A system according to claim 29, wherein the second plurality of station connection controllers are connected to incoming lines. 31. A system according to claim 30, wherein each incoming line is a ground start line. 32. A system according to claim 30, wherein the incoming lines are connected to the public switched network. 33. A system according to claim 32, wherein each incoming line is a ground start line. 34. A system according to claim 32, wherein each incoming line has a toll-free telephone number. 35. A system according to claim 34, wherein each incoming line is a ground start line. 36. A system according to claim 29, and further comprising means for originating calls from the system to the multi-purpose stations. 37. A system according to claim 36, wherein the means for originating calls from the system comprises means for generating number-representing signals in a sequence to identify a multi-purpose station. 38. A system according to claim 37, wherein the first plurality of station connection controllers are connected to outgoing lines connected to the public switched network, whereby the multi-purpose stations can be located in homes. 39. A system according to claim 37, wherein the means for originating calls from the system includes means for automatically redialing, whereby an interrupted call to a multi-purpose station can be re-established. 40. A system according to claim 37, wherein the means for originating calls from the system includes means operating automatically in an operation to replace an inactivated multi-purpose station, whereby an auxiliary attendant can be substituted to provide service. 41. A system according to claim 29, and further comprising in-band signal responsive means for controlling the second plurality of station connection controllers such that an attendant at a multi-purpose station can disconnect an incoming call yet remain off hook to be ready to have another incoming call extended to the off hook multi-purpose station. 42. A system according to claim 29, wherein the system is operable in traffic-volume dependent modes, and includes means operative during one such mode to release a multi-purpose station, then respond to a request to establish a call connection path for an incoming call by originating a call to, and re-establishing the previously released multi-purpose station as an attendant station, and then substantially simultaneously complying with the request and extending the incoming call to the re-established attendant station. 43. A system according to claim 42, wherein each of the second plurality of station connection controllers includes a ringing signal detection circuit for detecting such a request to establish a call connection path for an incoming call. 44. A system according to claim 43, wherein the ringing signal detection circuit produces a signal used to initiate a sequence of operations that are carried out while the ringing signal is present, and that thereby are transparent to the person placing the incoming call, by which an outgoing call is completed to a multi-purpose station and thereafter the incoming call is answered. 45. A system according to claim 29, wherein the first plurality of station connection controllers are connected to outgoing lines connected to the public switched network, whereby the multi-purpose stations can be located in homes. 46. A telecommunications control system for selectively networking a plurality of multi-purpose telephone stations for use as attendant stations in an attendant service complex to service calls directed to the system from originating stations, the system comprising: first controllable means comprising a plurality of outgoing line connection controllers, each outgoing line connection controller for cooperating with a respective one of a plurality of multi-purpose stations in defining opposite ends of a call connection path; second controllable means comprising a plurality of incoming line connection controllers, each incoming line station connection controller for cooperating with a respective one of a plurality of originating stations in defining opposite ends of a call connection path, and each including means for detecting a ringing signal indicating a request to establish a call connection path for an incoming call; third controllable means comprising a plurality of controllable inter-connection means, each arranged between an incoming line station connection controller and an outgoing line station connection controller; fourth controllable means for originating calls from the system to the multi-purpose stations via the outgoing line station connection controllers; and means for controlling the first, second, third, and fourth controllable means in a predetermined sequence of operations initiated by the detection of a ringing signal, in which sequence of operations a call is originated to a multi-purpose station while the ringing signal is present so as to be unnoticeable to a person using the originating station, and after completion of the call to the multi-purpose station, the incoming call is answered and extended to the multi-purpose station by completing the incoming call at the incoming line station connection controller and extending the call to the outgoing line station connection controller via the inter-connection means. 47. A system according to claim 46, wherein the means for originating calls from the system comprises means for generating number-representing signals in a sequence to identify a multi-purpose station. 48. A system according to claim 46, wherein the outgoing line station connection controllers are connected to the public switched network, whereby the multi-purpose stations can be located in homes. 49. A system according to claim 46, wherein the means for originating calls from the system includes means for automatically redialing, whereby an interrupted call to a multi-purpose station can be re-established. 50. A system according to claim 46, wherein the means for originating calls from the system includes means operating automatically in an operation to replace an inactivated multi-purpose station, whereby an auxiliary attendant can be substituted to provide service. 51. A computer-controlled system connectable between a set of incoming lines and a set of outgoing lines for using the outgoing lines to establish a network of multi-purpose stations for use by service attendants in servicing incoming calls directed to the system from originating stations via the incoming lines, the system comprising: controllable call extending means for connection between the incoming lines and the outgoing lines; computer processing means for controlling the controllable call extending means; the computer processing means including means providing digitally coded commands to control the call extending means and the call extending means including means providing status data to the computer processing means so the call extending means provides for extending incoming calls for answer and service by the service attendants; the call extending means comprising in-band signal detection means operative while a service attendant is servicing such a call for detecting the presence and source direction of an in-band signal; and the in-band signal detection means communicating with the means for providing status data to enable the computer processing means to initiate performance of control functions in response to the in-band signal. 52. A system according to claim 51, wherein the computer processing means responds to predetermined status data to control the call extending means to disconnect an incoming call as a result of an in-band signal received via an outgoing line without disconnecting a call connection path to the multi-purpose station via the outgoing line. 53. A system according to claim 51, and further comprising means controlled by the in-band signal detection means for providing security against use of a multi-purpose station by an unauthorized person. 54. A system according to claim 53, and further comprising means for playing a pre-recorded message to prompt an authorized person to initiate generation of a predetermined in-band signal. 55. A system according to claim 51, wherein the incoming lines are connected to the public switched network. 56. A system according to claim 55, wherein each incoming line is a ground start line. 57. A system according to claim 55, wherein each incoming line has a toll-free telephone number. 58. A system according to claim 57, wherein each incoming line is a ground start line. 59. A system according to claim 51, wherein the outgoing lines are connected to the public switched network, whereby the multi-purpose stations can be located in homes. 60. An interactively-supervised, computer-controlled system for allocating tasks in a network for servicing incoming calls, the system comprising: computer processing means; call extending means; the computer processing means including means providing digitally coded commands to the call extending means and the call extending means including means providing status data to the computer processing means so the call extending means provides for extending incoming calls for answer and service by a group of service attendants in accord with an allocation of tasks determined by the digitally coded commands; display means and manual input means for use by a supervisor in interactively controlling the computer processing means; the computer processing means being continually responsive to status data provided by the call extending means to generate on the display means a human-readable, continually-updated status report by which the supervisor may be prompted to use the manual input means to enter supervisory commands; and the computer processing means being responsive to such manually entered supervisory commands to provide digitally-coded commands to cause a re-allocation of tasks. 61. A system according to claim 60, wherein the computer processing means is responsive to a supervisory command to transfer an incoming call in progress, such that the task of servicing the incoming call is reallocated. 62. A system according to claim 60, wherein the computer processing means is responsive to a supervisory command to discontinue extending calls to a designated service attendant, such that the tasks of answering and servicing incoming calls that would otherwise have been allocated to the designated agent are reallocated. 63. A system according to claim 60, wherein the computer processing means includes means responsive to status data for accumulating a statistical data base. 64. A system according to claim 63, wherein the computer processing means is responsive to a supervisory command to display a selected report of data in the statistical data base. 65. A system according to claim 60, and further comprising means for use by the supervisor in selectively participating in a call. 66. A system according to claim 60, and further comprising means for use by the supervisor in selecting a call to monitor. 67. A system according to claim 60, and further comprising means for enabling a service attendant to initiate an operation that automatically communicates a prompt to the display means. 68. A system according to claim 60, and further comprising means for enabling a service attendant to initiate an operation that automatically communicates an audible prompt. 69. A system according to claim 60, wherein the call extending means includes means for causing a plurality of incoming calls to be extended to the same service attendant during an interval throughout which the service attendant is continuously on line to the system. 70. A system according to claim 60, wherein the call extending means is connected to incoming lines connected to the public switched network. 71. A system according to claim 70, wherein each incoming line is a ground start line. 72. A system according to claim 70, wherein each incoming line has a toll-free number. 73. A system according to claim 72, wherein each incoming line is a ground start line. 74. A system according to claim 60, wherein the call extending means is connected to outgoing lines. 75. A system according to claim 74, wherein the outgoing lines are connected to the public switched network, whereby a service attendant can service calls at home. 76. A system according to claim 60, and further comprising means for originating calls from the system to the service attendant. 77. A system according to claim 76, wherein the means for originating calls from the system comprises means for generating number-representing signals in a sequence to identify a multi-purpose station. 78. A system according to claim 77, wherein the call extending means is connected to outgoing lines connected to the public switched network, whereby the multi-purpose stations can be located in homes. 79. A system according to claim 77, wherein the means for originating calls from the system includes means for automatically redialing, whereby an interrupted call to a multi-purpose station can be re-established. 80. A system according to claim 77, wherein the means for originating calls from the system includes means operating automatically in an operation to replace an inactivated multi-purpose station, whereby an auxiliary attendant can be substituted to provide service. 81. A modular line card for use in a telecommunications control system for networking a plurality of multi-purpose stations for use as attendant stations in an attendant service complex to service calls directed to the system from originating stations, the system being connected to a plurality of lines for incoming calls and to a plurality of lines for outgoing calls and having a system bus, the modular line card comprising: means for connecting to the bus; a first station connection controller for connection to one of the incoming lines for cooperating with a respective one of a plurality of multi-purpose stations in defining opposite ends of a call connection path; a second station connection controller for connection to one of the outgoing lines for cooperating with a respective one of a plurality of originating stations in defining opposite ends of a call connection path; controllable inter-connection means arranged between the first and second station connection controllers; and means for controlling the inter-connection means such that incoming calls from originating stations are extended to multi-purpose stations that have been networked for use as attendant stations, and wherein the means for controlling the inter-connection means includes means for causing a plurality of incoming calls to be extended to the same multi-purpose station during an interval throughout which the multi-purpose station remains networked as an attendant station. BACKGROUND OF THE INVENTION This invention relates to telephone communications control systems. Many organizations gather and distribute information in the course of telephone calls serviced at least in part by members of a staff of attendants. Such organizations include major corporations which conduct television or other media advertising campaigns to encourage customers and potential customers to call the organization via a telephone number that is toll-free to the caller. The area code "800" is used in the United States for such toll-free telephone numbers. As for gathering and distributing information, this typically entails having a service attendant elicit the caller's name and address and some kind of ordering information for goods or services and then provide information such as price and delivery information. In some of the many varied situations, the organization is providing "help" to a customer concerning use of the organization's goods or services, including goods such as retail computer programs and services such as repair or maintenance services under a warranty. Other such organizations include non-commercial public broadcasting stations which solicit contributions from the viewing public to defray the cost of providing the broadcast services. Typically, such stations receive volunteer help from a large group of people who serve as an attendant staff to service incoming calls. Often during such fund raising telecasts, the public broadcasting station shows not only the persons who encourage viewers to call, but also the staff of service attendants who occupy desks on a stage and use telephone station sets specifically dedicated for use by the attendants in servicing incoming calls. As to commercial television stations, they often broadcast telethons to raise money for charity and likewise need a large group of people to service incoming calls. Religious and other non-commercial organizations also use telecasts to encourage viewers to call the organization to receive pamphlets and other materials of interest. In each of the above-described situations, there is a need to provide, in a systematic and orderly way, for prompt and efficient servicing of the calls. Providing attendant service for multiple incoming calls at the same time requires multiple incoming lines. Unless a sufficient number of incoming lines are provided to meet the needs of peak volume traffic, incoming callers will have to wait for service, and the longer the wait, the higher the percentage of callers who will hang up before receiving service. A tariff charge must be paid by the subscriber for every incoming line. Further, if the incoming line is one which provides for toll-free dialing, the subscriber must pay usage charges for the line. Thus, a substantial expense can be incurred in subscribing to and using many lines. It is highly desirable to minimize the percentage of time that is spent on what can be categorized as overhead time, such as time spent in completing a connection between an incoming line allocated to a call request and a line to an attendant station. As a result of advances in technology, particularly in digital data processing and digital switching techniques, and as a result of substantial efforts in research and development, various electronic systems have been developed to perform complex functions in controlling telephone communications lines. These electronic systems include very powerful PABXs (private automatic branch exchanges), ACDs (automatic call distributors), and the like. An ACD system is designed to perform functions to provide for uniformly distributing incoming calls among members of an attendant service staff. Another type of electronic system that is of interest as background is disclosed in U.S. Pat. No. 3,859,473 to Brown et al., titled "Centralized Attendant Service Arrangement for PABX Complex." An object of the system Brown et al. disclose is to provide a centralized attendant service (CAS) arrangement which permits all incoming calls to a complex of PABXs to be handled at a single attendant position location. Another type of electronic system that is of interest as background is disclosed in U.S. Pat. No. 3,881,060 to Connell et al., titled "Emergency Reporting System. " The system Connell et al. disclose is directed to providing features to facilitate routing of incoming calls originated by dialing a universal emergency number, such as "911," to a selected community emergency service center. The incoming calls are routed on the basis of where the originating station is located so that each such emergency call is answered at the community emergency center that serves that location. Despite these advances in technology and despite the substantial effort in research and development, there has continued to be a need for a system to facilitate handling multiple incoming calls, in an efficient way. SUMMARY OF THE INVENTION This invention provides a novel and advantageous system for meeting the need to facilitate handling multiple calls entering the system in an efficient way. The invention may be defined in various terms. According to one definition of the present invention, it resides in a telecommunications control system for accepting a plurality of multi-purpose stations for use as attendant stations in an attendant service complex to service calls directed to the system from originating stations. This system comprises a first plurality of connection controllers. Each connection controller in this first plurality of connection controllers provides for cooperating with a respective one of a plurality of multi-purpose stations in defining opposite ends of a call connection path. Each of these connection controllers has controllable switching means for opening the call connection path and releasing the respective multi-purpose station. The system includes means for providing security against use of any of the multi-purpose stations within the attendant service complex by an unauthorized person. The security-providing means includes means for controlling the switching means to open the call connection path and release the multi-purpose station. This system further includes a second plurality of connection controllers. Each connection controller in this second plurality of connection controllers provides for cooperating with a respective one of a plurality of originating stations in defining opposite ends of a call connection path. This system further includes controllable inter-connection means arranged between the first and second plurality of connection controllers, and includes means for controlling the inter-connection means such that incoming calls from originating stations are extended to multi-purpose stations that have been accepted as attendant stations. Numerous advantages of the above-described system flow from those features adapting it to cooperate with multi-purpose stations. For example, there is no need to make an extra investment to acquire stations to be dedicated solely to this system. Such an extra investment is particularly substantial in the case of an order-entry system or the like in which the multi-purpose stations involve more cost than an ordinary telephone set as is the case for multi-purpose stations that include video display terminals or the like and related equipment such as modems for telecommunication of data via the system. Further, the system does not place any constraint on where the multi-purpose stations are to be located. To the contrary, according to a particularly preferred feature, the first plurality of connection controllers are connected to outgoing lines connected to the public switched network, whereby the multi-purpose stations can be located in homes. Taken in combination with the feature as to multi-purpose stations, the security-providing feature of the above-described system is particularly advantageous. Preferably, the security-providing means includes means for receiving a security clearance signal via the call connection path to a multi-purpose station. In the presently preferred embodiment of the system, as described in detail below, the system has automatic dialing circuitry used to originate calls to multi-purpose stations. When the call originated by the system to the multi-purpose station results in the multi-purpose station going on line, as for example when an authorized person takes the handset of a multi-purpose telephone station off hook, the authorized person uses the station keypad to input a code defining the security clearance signal which is transmitted in DTMF (dual tone multi frequency) signal form to the system. The preferred embodiment includes means for receiving the security clearance signal and converting it to a logic signal. The logic signal cooperates with a timing means in the system. If such logic signal is not defined within a predetermined timing interval, the system automatically releases the multi-purpose station so that it will not be accepted for use as an attendant station in the attendant service complex. According to another definition of the invention, it resides in a system for networking such a plurality of multi-purpose stations in an attendant service complex. To provide for such networking, the system includes connection controllers arranged into a first plurality and a second plurality, with the first plurality providing for cooperating with multi-purpose stations and with the second plurality cooperating with originating stations. Controllable inter-connection means are arranged between the first and second plurality of connection controllers. In accord with a highly advantageous feature, the system for networking includes means for controlling the inter-connection means such that incoming calls from originating stations are extended to multi-purpose stations that have been networked for use as attendant stations with such controlling means including means for causing a plurality of incoming calls to be extended to the same multi-purpose station during an interval throughout which the multi-purpose station remains networked as an attendant station. This highly advantageous feature significantly reduces overhead time. Particularly when incoming traffic is high, it is highly desirable to extend one incoming call after another to an attendant station with minimum interruption. In a system such as the preferred embodiment of this invention where the networked multi-purpose stations can be at any location serviced by the public switching network, a relatively large amount of time is required to carry out a call connection operation. An amount of time in the order of 10 seconds or more is quite significant in this context, particularly when considered in light of high volume traffic where it is desirable to completely service the calls within an average time span in the order of a couple of minutes. To minimize line usage charges even further, the presently preferred embodiment of this invention is operable in traffic volume dependent modes, and includes means operative during one such mode to release a multi-purpose station, then respond to a request to establish a call connection path for an incoming call by originating a call to, and re-establishing the previously released multi-purpose station as an attendant station, and then substantially simultaneously complying with the request in extending the incoming call to the re-established attendant station. Usage charges for both outgoing and incoming lines are reduced because of this feature. As to outgoing lines, the reduction in usage charges is a function of the average duration of a call compared to the average duration between calls. As to incoming lines, because in this sequence the multi-purpose station is re-established as a network station before responding to the request, usage charges for the expensive incoming lines such as "800" lines are reduced. According to another definition of the present invention, it resides in an interactively-supervised, computer-controlled system for allocating tasks in a network for servicing incoming calls. The system comprises computer processing means and call extending means. The computer processing means includes means providing digitally coded commands to the call extending means and the call extending means includes means providing status data to the computer processing means so that the call extending means provides for extending incoming calls for answer and service by a group of service attendants in accord with an allocation of tasks determined by the digitally coded commands. The system further includes display means and manual input means for use by a supervisor in interactively controlling the computer processing means. The computer processing means is continually responsive to status data provided by the call extending means to generate on the display means a human-readable, continually updated status report by which the supervisor may be prompted to use the manual input means to enter supervisory commands. The computer processing means is responsive to such manually entered supervisory commands to provide digitally coded commands to cause a reallocation of tasks. The foregoing and other novel and advantageous features of this invention are described in detail below and are recited in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an overall general functional block diagram of a system embodying preferred features of the invention to provide for interactively supervising a computer-controlled sub-system to allocate tasks in a network for servicing incoming calls; FIG. 2 is an annotated map indicating a representative, geographically-dispersed configuration of a system embodying a preferred feature of the invention whereby the public switched network is used to extend calls to multi-purpose stations located in various parts of the United States; FIG. 3 is a functional block diagram illustrating a modular organization of electronic equipment incorporated in the preferred embodiment; FIG. 4 shows mechanical features of the modular organization; FIG. 5 is a block and schematic diagram of a bus controller incorporated in each of a series of rows of a line connection sub-system rack mounted in a cabinet in the preferred embodiment; FIG. 6 is a block and schematic diagram of circuitry included on a communications card used in the preferred embodiment; FIG. 7 is a block and schematic diagram of circuitry for a supervisory station connection controller included on a monitor card used in the preferred embodiment; FIG. 8 is a block and schematic diagram of sequencing circuitry for the monitor card; FIG. 9 is a block and schematic diagram of command-decoding circuitry for the monitor card; FIG. 10 is a block and schematic diagram of a circuit arrangement that is replicated on an audio message card used in the preferred embodiment for generating and transmitting messages; FIG. 11 is a block and schematic diagram of a circuit arrangement, similar in most respects to that of FIG. 10, and having additional circuitry used for digitizing an audio message and storing the digitized message in a RAM; FIG. 12 is a block and schematic diagram of command-decoding circuitry for the audio message card; FIG. 13 is a block and schematic diagram of circuitry on the audio message card for providing status data; FIG. 14 is a general functional block diagram of a line card used in the present invention for each pair of incoming and outgoing telephone lines; FIG. 15 is a block and schematic diagram of a portion of the line card, and shows circuitry for a pair of connection controllers and an inter-connection switch; FIG. 16 is a block and schematic diagram of another portion of the line card, and shows circuitry for implementing an audio interface incorporating audio selection switches; FIG. 17 is a block and schematic diagram of another portion of the line card, and shows circuitry for controlling audio selection switches; FIG. 18 is a block and schematic diagram of another portion of the line card, and shows sequencing circuitry for the connection controller for the outgoing line; FIG. 19 is a block and schematic diagram of another portion of the line card, and shows sequencing circuitry for the connection controller for the incoming line; FIG. 20 is a block and schematic diagram of another portion of the line card, and shows circuitry for DTMF number generation and in-band signal decoding; FIG. 21 is a block and schematic diagram of another portion of the line card, and shows command-decoding circuitry; FIG. 22 is a block and schematic diagram of another portion of the line card, and shows circuitry for providing status data; FIG. 23 shows a representative displayed status report for a supervisor at a supervisory console; FIG. 24 shows a top portion of a displayed status report, in which a pull-down menu appears as a result of the selection of "Change"; FIG. 25 is related to FIG. 24, and shows a pull-out menu resulting from a selection of "Call" from the pulldown menu; FIG. 26 shows another representative displayed status report, in which a pull-down menu appears as a result of the selection of "Info"; FIG. 27 is related to FIG. 26, and shows a portion of the displayed status report in which the supervisor is being prompted to confirm a change in a phone number; FIG. 28 shows a top portion of a displayed status report, in which a pull-down menu appears as a result of the selection of "Shifts"; FIG. 29 comprises FIGS. 29A and 29B, and is a general flow chart of overall operations involved in one of three processes carried out by a supervisory computer in the presently preferred embodiment, each of the three processes operating independently of one another; the process of FIG. 29 being for communications between the supervisory computer and a controlling computer incorporated in the presently preferred embodiment; FIG. 30 is a general flow chart of overall operations involved in a second of the three processes carried out by the supervisory computer, the process of FIG. 30 being for real-time timing and for automatic functions; FIG. 31 is a general flow chart of overall operations involved in the third of the three processes carried out by the supervisory computer, the process of FIG. 31 being for the user interface; FIG. 32 comprises FIGS. 32A and 32B, and is a more detailed flow chart of certain operations involved in the process of FIG. 31 with respect to processing a user command to send to the controlling computer; FIG. 33 comprises FIGS. 33A and 33B, and is a more detailed flow chart of certain operations involved in the process of FIG. 31 with respect to processing a system configuration command; FIG. 34 comprises FIGS. 34A and 34B, and is a more detailed flow chart of certain operations involved in the process of FIG. 31 with respect to processing shift and operator commands; FIG. 35 is a general flow chart of overall operations involved in a main, outer loop carried out by the controlling computer; FIG. 36 is a more detailed flow chart of certain operations generally referred to in FIG. 35, in particular operations for processing commands from the supervisory computer; FIG. 37 is a more detailed flow chart of certain operations generally referred to in FIG. 36, in particular operations for servicing incoming telephone number commands; FIG. 38 is a more detailed flow chart of certain operations generally referred to in FIG. 36, in particular operations for servicing line control commands; FIG. 39 is a more detailed flow chart of certain operations generally referred to in FIG. 38, in particular operations for servicing a call-attendant command; FIG. 40 is a more detailed flow chart of certain operations generally referred to in FIG. 38, in particular operations for servicing a disconnect-attendant command; FIG. 41 is a more detailed flow chart of certain operations generally referred to in FIG. 36, in particular operations for servicing monitor control commands; FIG. 42 comprises FIGS. 42A and 42B, and is a more detailed flow chart of certain operations generally referred to in FIG. 36, in particular operations for servicing a configuration command; FIG. 43 is a more detailed flow chart of certain operations generally referred to in FIG. 36, in particular operations for servicing help and emergency commands; FIG. 44 is a more detailed flow chart of certain operations generally referred to in FIG. 43, in particular operations for transferring an incoming caller; FIG. 45 is a more detailed flow chart of certain operations generally referred to in FIG. 35, in particular operations for scanning for line card status changes; FIG. 46 is a more detailed flow chart of certain operations generally referred to in FIG. 35, in particular operations for the processing of status changes; FIG. 47 comprises FIGS. 47A and 47B, and is a more detailed flow chart of certain operations generally referred to in FIG. 46, in particular operations for processing of status changes; FIG. 48 is a more detailed flow chart of certain operations generally referred to in FIG. 47A, in particular operations carried out upon determining that the outgoing line is back on hook; FIG. 49 is a more detailed flow chart of certain operations generally referred to in FIG. 47A, in particular operations for processing of DTMF status changes; FIG. 50 is a more detailed flow chart of certain operations generally referred to in FIG. 49, in particular operations to service a DTMF help request; FIG. 51, is a more detailed flow chart of certain operations generally referred to in FIG. 49, in particular operations to service a DTMF cancel request; FIG. 52 is a more detailed flow chart of certain operations generally referred to in FIG. 49, in particular operations to service a DTMF emergency request; FIG. 53 is a more detailed flow chart of certain operations generally referred to in FIG. 49, in particular operations carried out if an attendant refuses calls; FIG. 54 is a more detailed flow chart of certain operations generally referred to in FIG. 49, in particular operations to service a DTMF activation for another call; FIG. 55 is a more detailed flow chart of certain operations generally referred to in FIG. 49, in particular operations to service a DTMF response from an emergency attendant; FIG. 56 is a more detailed flow chart of certain operations generally referred to in FIG. 47B, in particular operations carried out if an incoming caller has hung up; FIG. 57 is a more detailed flow chart of certain operations generally referred to in FIG. 56, in particular operations involved when a transfer has been attempted; FIG. 58 is a more detailed flow chart of certain operations generally referred to in FIG. 56, in particular operations involved other than when a transfer has been attempted; FIG. 59 is a more detailed flow chart of certain operations generally referred to in FIG. 47B, in particular operations carried out if an attendant has hung up; FIG. 60 comprises FIGS. 60A and 60B, and is a more detailed flow chart of certain operations generally referred to in FIG. 59, in particular operations involved when a transfer has been attempted; FIG. 61 comprises FIGS. 61A and 61B, and is a more detailed flow chart of certain operations generally referred to in FIG. 59, in particular operations involved other than when a transfer has been attempted; and FIG. 62 is a more detailed flow chart of certain operations generally referred to in FIG. 46, in particular operations for dumping an internal line database to the supervisory computer. DETAILED DESCRIPTION FIG. 1 shows, in general block diagram form, major functional elements of an interactively-supervised, computer controlled system 1A organized in accord with the presently preferred embodiment of this invention. System 1A provides for allocating tasks in a network for servicing incoming calls arriving on a plurality of incoming telephone lines 1B such as incoming line 1B-1. System 1A comprises a line connection sub-system 1C arranged between incoming telephone lines 1B and a plurality of outgoing telephone lines 1D such as line 1D-1. System 1A further comprises a computer processing sub-system 1E which digitally communicates with line connection subsystem 1C. In digitally communicating with line connection sub-system 1C, computer processing sub-system 1E provides digitally coded commands and receives status data. Through such digital communication, line connection sub-system 1C cooperates with computer processing sub-system 1E and operates under its control to provide a call extending controller 2A (FIG. 2) capable of operating on an autonomous basis to extend incoming calls for answer and service by a group of people working as service attendants in accord with an allocation of tasks determined by the digitally coded commands. System 1A further includes a display means such as a video display terminal 1F and manual input means such as a mouse 1G for use by a person designated as a supervisor in interactively controlling computer processing sub-system 1E. A keyboard 1H is part of video display terminal 1F, and may also be used by a supervisor who prefers to enter supervisory commands by keyboard entry rather than through mouse IG. A supervisory station 1I is connected via a monitor phone line 1J to line connection sub-system 1C to provide an audio link that the supervisor uses to confer with an incoming caller, with one or more service attendants, or with an incoming caller and a service attendant simultaneously. In system 1A, supervisory station 1I is a conventional touch-tone dial telephone instrument with a microphone and speaker for optional hands-free talking and listening; one of numerous alternatives involves using a headset as supervisory station 1I. In combination, supervisory station 1I, video display terminal 1F, and mouse 1G provide a supervisory console generally indicated as 1K. Computer processing sub-system 1E is continually responsive to status data provided by line connection sub-system 1C to generate on video display terminal 1F a human-readable, continually updated status report by which the supervisor may be prompted to use mouse 1G to enter supervisory commands. Computer processing sub-system 1E is responsive to such manually entered supervisory commands to provide digitally coded commands to cause a re-allocation of tasks, as explained more fully below with reference to more detailed drawings concerning the construction and operation of system 1A. One of the advantages of the present invention is that the above-described major functional elements and the manner in which they cooperate are such that system 1A can be set up in any of a variety of configurations to suit the needs of any particular organization and facilitate the handling of multiple incoming calls in an efficient way. With respect to computer processing sub-system 1E, the functions it performs divide in a general way into functions relating to communicating with and controlling line connection sub-system 1C whereby incoming calls can be autonomously extended, and into functions relating to communicating with and controlling video display terminal 1F whereby human readable status reports can be displayed and the supervisor can interactively exercise human control over system functions. A suitable, and presently preferred, configuration of computer processing sub-system 1E entails two physically separate microprocessor-controlled computers of the kind commonly described as personal computers, and a data communication link between the two personal computers. Herein, one of these personal computers is referred to as a controlling computer, and the other as a supervisory computer. With such presently preferred configuration, the controlling computer operates under software control to cooperate with line connection sub-system 1C to define call extending controller 2A (FIG. 2) which extends incoming calls to service attendants on an autonomously operating basis. It should be understood that the physical division of computer processing sub-system 1E into two separate personal computers is a subordinate detail. It would be suitable, for example, to employ a so-called "dumb terminal" with which a supervisor interacts with the system, and to concentrate computer processing functions within a single computer. With reference to FIG. 2, there will now be described a representative overall system configuration, set up for an organization having facilities in Dallas, Tex. and an office in Chicago, Ill. The representative configuration of FIG. 2 takes advantage of particularly preferred features of a system embodying the invention, whereby the incoming lines and the outgoing lines are connected to the public switched network. Because the incoming lines are connected to the public switched network, through a central office 2B near the Dallas facilities, a caller can originate an incoming call to the system from any arbitrary location, e.g., New York City as indicated in FIG. 2, with the incoming call being routed through a nearby central office 2C over the public switched network to central office 2B. The organization can subscribe to a group of incoming toll-free lines, all appearing to have the same "800" telephone number. The routing of any incoming call, originated by dialing the "800" number, is effected in accord with the standard techniques of the public switched network. Because the outgoing lines are connected to the public switched network, incoming calls can be extended to various arbitrary locations, including private homes where ordinary home telephones can be used by a part-time staff of at-home service attendants to answer and service the calls. For example, one of the part-time staff of at-home service attendants can answer and service calls extended by system 1A through the public switched network to Seattle, Washington, as indicated in FIG. 2. Because of the three-hour difference between the time zones for the East Coast and the West Coast, it often will be desirable to take this time difference into account in forming a shift of at-home service attendants. Thus, when a high volume of incoming calls are likely to be placed from locations in the East Coast in the early morning there, say between 6:00 a.m. and 7:00 a.m., it is more desirable for the staff of at-home service attendants to be selected from residents along the East Coast. As to the person who is to serve as the supervisor of the system, that person likewise can work at any arbitrary location, e.g., in the organization's offices in Chicago. In accord with preferred features of this invention, modems (not shown in FIG. 2) are provided to communicate data over the public switched network between call extending controller 2A located in Dallas and supervisory console 1K located in Chicago. Further with respect to overall operation of system 1A, it is highly desirable for it to provide features making efficient use of the investment made in the system and in leasing telephone lines, and to minimize telephone usage charges, both with respect to usage charges for the incoming lines that are toll free only to the originating parties, and with respect to usage charges for the outgoing lines. To provide for such efficiency, it is advantageous for the system to include automatic dialing features to place calls to a group of multi-purpose stations such as at-home telephones, and accept these called stations as network stations, all just before the beginning of any period of predictable high volume incoming traffic. System 1A has such preferred automatic dialing features as disclosed in more detail below, and has further novel and advantageous features relating to accepting multi-purpose stations into the network or complex of attendant service stations, and relating to performing this function in a highly automated way. As part of this automation, system 1A provides automatic message transmitting features, whereby service attendants upon answering the call automatically placed by the system are greeted with a pre-recorded message, alerting them that the call being answered is one from the system, and thereby prompting the entry of a code defining a security clearance signal which is transmitted in DTMF (Dual Tone Multi Frequency) signal form to system 1A. System 1A provides for transmitting numerous other messages under various circumstances, such as at the end of a shift; for transmitting music, for example, while a service attendant is waiting to have an incoming call extended; and for transmitting a prompt tone to the service attendant just before an incoming call is to be extended. With reference to FIG. 3, system 1A will now be described at a more detailed block diagram level. To emphasize basic features of system 1A and to avoid obscuring such basic features with subordinate detail, various matters concerning the construction of this specific embodiment are referenced in FIG. 3 in general terms. One such matter concerns a matrix of line cards referenced in FIG. 3 in general terms as line card 3A(0,1) through line card 3A(M,N), where M stands for row and N stands for column. In a specific embodiment, particularly suitable for handling a high volume of incoming traffic, there are 105 line cards arranged in seven rows (0 . . . 6) and fifteen columns (1 . . . 15). The line cards form part of line connection subsystem 1C that is appropriately characterized as a hardware sub-system. In addition to the line cards, sub-system 1C includes a separate row bus corresponding to each row of line cards, including row (0) bus, row (1) bus, and row (M) bus. Sub-system 1C further includes a separate bus controller corresponding to each row bus, including bus controller (0), bus controller (1), and bus controller (M). Sub-system 1C further includes a system bus, and a plurality of system cards. As presently arranged, the specific embodiment has the capacity to receive up to seven different system cards, including such system cards as may be provided in future expansion to provide special functions that may be desired. One of the system cards that is used in this specific embodiment is a SYS. CARD 0, which is also referred to as communications card 3B. FIG. 3 also shows a controlling computer 3C which communicates with line connection sub-system 1C through communications card 3B. Communications card 3B has an asynchronous communications interface for communicating with controlling computer 3C. FIG. 3 also shows supervisory console 1K as comprising a remote supervisory computer 3D and supervisory station 1I. A modem phone line 3E connects remote supervisory computer 3D to controlling computer 3C. Controlling computer 3C has an internal modem which is connected via modem phone line 3E to a remote modem within remote supervisory computer 3D. Another one of the system cards, viz, SYS. CARD 1 (also referred to as monitor card 3F) communicates with supervisory station 1I via monitor phone line 1J. Another one of the system cards, viz, SYS. CARD 2 (also referred to as audio message card 3G) provides circuitry used in automatic message transmitting features of system 1A. Each line card has an incoming line interface, an outgoing line interface, and a row bus interface. Line card 3A(0,1) has its incoming line interface connected to incoming line 1B-1, and has its outgoing line interface connected to outgoing line 1D-1. In general, any line card can be referred to as line card 3A(i,j), and in accord with such general terminology, such line card 3A(i,j) has its incoming line interface connected to incoming line 1B-[(i*15)++j] and its outgoing line interface connected to outgoing line 1D-[(i*15)+j]. Each of the line cards along a row has its row bus interface connected to the particular row bus of row bus (0) through row bus (M) that corresponds to that row. All the bus controllers and all the system cards connect directly to the system bus. FIG. 4 shows the line cards in place within a cabinet 4A that is a standard size cabinet for housing rack-mounted printed circuit boards. Within cabinet 4A there are seven backplane or motherboards 4B-0 through 4B-M, each extending across the width of cabinet 4A. In accord with conventional techniques, each line card has an edge connector for connection to a mating, vertically oriented connector on such a motherboard. As indicated in FIG. 4, the fifteen line cards of each row are horizontally spaced apart within cabinet 4A. Each motherboard has, in addition to the fifteen connectors for a row of line cards, another connector for a system card. As indicated above, each system card communicates with the system bus. Each motherboard also supports circuitry (FIG. 5) for implementing the functions of the bus controller for the corresponding row. To provide a further general overview of the entire system before proceeding into a detailed disclosure of specific implementing hardware, there will now be described, with reference to FIG. 23, a representative human-readable status report that is displayed to the supervisor. This representative displayed status report, like others described below, has a format suitable for presentation on a standard 25-line monochrome display, but preferably is displayed on a color display so that easily remembered color codes can facilitate prompting of the supervisor. The top line of the displayed status report is referred to herein as a main menu selection line. Any item on the main menu selection line can be selected by the supervisor by moving mouse 1G so as to position a mouse cursor to the desired item and clicking a button on the mouse. Some of the main menu items have associated sub-menus (not shown in FIG. 23), each of which presents sub-selections in a pull-down menu upon selection of a main menu item. Further, some sub-selections on certain pull-down menus have associated options that are presented as a pull-out menu as explained more fully below. The main menu items appearing on the representative displayed status report of FIG. 23 are "Change," "Info," "Shifts," "Symbols," "Numbers," and "Monitor." Beneath the main menu selection line there is an area that in the representative displayed status report of FIG. 23 sets out what can be categorized as "global information." This global information includes the current date and time and information concerning a "shift"; i.e., information identifying, as a group, the people who are serving as service attendants, and statistical information ("Total calls" and "Total Drops") concerning the performance of the system. Beneath the global information area is a legend line showing six items, viz, "Dialing," "Not Ready," "Ready," "WATS Call," "Made Busy," and "Forward." Each of these items is displayed with a color-coded box to aid the supervisor in interpreting color coding of the displayed status report. Beneath the legend line there is a matrix display area that in this specific embodiment has 105 elements that are in one-to-one correspondence with the 105 line cards mentioned above. Each of the elements in the matrix display area comprises a box and an optional line card number. Each box provides status information concerning a corresponding line card; preferably this is provided by color coding the boxes. In FIG. 23, each box is shaded for the color blue, this being the color used to indicate a line card condition in which there is no attendant on line, and software has made the line card idle by "busying" its incoming line. Other colors, not shown in FIG. 23, are: bright red to indicate that the attendant is not ready to service an incoming call; yellow to indicate that the attendant is waiting for an incoming call; green to indicate that the attendant is servicing an incoming call; and grey to indicate that, during a particular mode, referred to hereafter as call forward mode, the attendant is not on line. One box at a time is surrounded by a frame that serves as a display pointer to a line card. In FIG. 23, the display pointer happens to be framing the box numbered "77." This means that the supervisor can issue supervisory commands targeted to affect the line card that has a line card ID of "77." If the supervisor wants to issue supervisory commands targeted to affect a different line card, the supervisor can move mouse 1G to position the mouse cursor at the desired box, then click the mouse button, and the display pointer will jump to the selected box. If the supervisor desires to erase the line card ID numbers that appear in this displayed report, the supervisor can position the mouse cursor to the "Numbers" item on the main menu selection line, then click the mouse cursor button, and the line card ID numbers will be erased. The "Numbers" item on the main menu selection line constitutes a toggle-type selection; i.e., successive selections of this item toggles the numbers on and off. If the supervisor desires to be prompted by symbols instead of color coding (as when a monochrome display is being used), the supervisor can position the mouse cursor to the "Symbols" item on the main menu selection line, then click the mouse button, and status-representing symbols will replace the color-coded boxes in the matrix and in the legend line. Like the "Numbers" item, the "Symbols" item is a toggle. Another toggle item is the "Monitor" item. Successive selections of this item toggle between an incoming line monitor and an outgoing line monitor. The status of the monitor item toggle is also visually displayed; in the preferred embodiment, the display pointer is a single line frame in one case, and a double line frame in another case. There is no need for any pull-down menu for any of the toggle items. With reference to FIGS. 5 and 6, there will now be described circuitry involved in communicating digitally coded commands and status data, and audio, between controlling computer 3C and sub-system 1C. FIG. 5 shows circuitry for implementing a bus controller; as stated above, each motherboard has such a bus controller. FIG. 6 shows circuitry for implementing communications card 3B. Each bus controller has essentially the same construction, and, for generality of reference, circuitry shown in FIG. 5 is identified therein as "BUS CONTROLLER (I)." This circuitry is connected between the system bus and row bus (I). The system bus has 42 parallel conductors. Six of these parallel conductors are referred to as an Audio Bus which provides for propagating signals identified as Message 1, Message 2, Message 3, Message 4, Music, and Monitor Audio. The purposes of these signals have been generally described above as part of the general overview of the system and various features it provides including automatic message transmission features, etc. Each row bus has six corresponding parallel conductors, and each bus controller directly connects together the Audio Bus portion of the system bus and the Audio Bus portion of the row bus. This is indicated in FIG. 5 by the line labelled "Audio Bus" that extends between the lines labelled "SYSTEM BUS" and "ROW BUS (I)." The number of parallel conductors in the Audio Bus is indicated in FIG. 5 by a slash and the number 6 next to the slash. This symbology of a slash and an adjacent number is used throughout the drawings to indicate the number of parallel conductors that are represented as a single line. Eight other parallel conductors of the system bus provide for propagating a Command Word. In FIG. 5, a functional block 5A is used to indicate that eight parallel Schmitt trigger drivers are included in each bus controller for communicating each such Command Word to the corresponding row bus. Eight other parallel conductors of the system bus provide for propagating a Status Word. As indicated in FIG. 5, a tri-state bus driver 5B is included in each bus controller for selectively communicating a Status Word from the corresponding row bus to the system bus. Eight other parallel conductors of the system bus are referred to as a Row Select Bus which provides for propagating a one-out-of-eight selection signal. As indicated in FIG. 5, each bus controller has a row address selector 5C comprising a group of terminal pairs with which a jumper 5D is used to configure a row address. It should be understood that one of these eight conductors is a spare providing for system expansion from the seven-row matrix of cards used in the specific embodiment being described. Four other parallel conductors of the system bus provide for propagating a Card Select Nibble. As indicated in FIG. 5, a decoder 5E is included in each bus controller for decoding the Card Select Nibble. Decoder 5E has an enable input connected to the output of an AND gate 5F. If the output of AND gate 5F is true, and a Card Select Nibble is applied to decoder 5E, then one of sixteen Card Select signals will be true. A Card Select 0 signal selects a system card within a row. Each of the remaining fifteen such card select signals selects a line card within a row. One other conductor of the system bus provides for propagating a Row Bus Disable Flag produced by a retriggerable one-shot 5G in response to manual actuation of a row service switch 5H. One other conductor of the system bus provides for propagating a 3.579 MHz Clock signal. Each bus controller has a Schmitt trigger driver 5I for propagating this clock signal to the corresponding conductor of the row bus. One other conductor of the system bus provides for propagating a Prompt Tone signal. The Prompt Tone signal is used for the purpose, generally described within the general overview of the system, of prompting a service attendant to be prepared to service an incoming call; the Prompt Tone signal is automatically transmitted over an outgoing line just before an incoming call is extended for answer and service by the service attendant. Suitably, the Prompt Tone signal has a frequency of 400 Hz. Each bus controller has a Schmitt trigger driver 5J for propagating this Prompt Tone signal to the corresponding conductor of the row bus. One other conductor of the system bus provides for propagating a Message 2 Start/Stop Strobe signal. Each bus controller has a Schmitt trigger driver 5K for propagating this strobe signal to a corresponding conductor of the row bus. Four other conductors of the system bus define a spare bus providing for system expansion. As shown in FIG. 6, communications card 3B includes a UART (Universal Asynchronous Receiver Transmitter) 6A having an "S In" input for receiving serial input data (from controlling computer 3C) and having an "S Out" output for transmitting serial output data (to controlling computer 3C). A baud rate generator 6B and a crystal 6C tuned to 1.8432 MHz cooperate to provide an input control signal to UART 6A to set its baud rate. With respect to the serial input data UART 6A receives, UART 6A performs a serial-to-parallel conversion function such that each group of eight successive bits of a byte are converted to parallel format and applied to an eight-conductor signal path 6A-0. With respect to the serial output data UART 6A transmits, UART 6A performs a parallel-to-serial conversion function such that each eight-bit Status Word it receives in parallel from the system bus via a signal path 6A-I is converted to serial form for transmission to controlling computer 3C. Communications card 3B further includes an 8-bit address latch 6D, an 8-bit command word latch 6E, and a 3.times.8 decoder 6F that are arranged to respond to the parallel output of UART 6A; and further includes a divider 6G that performs a frequency dividing function in response to an output of generator 6B to produce the Prompt Tone at approximately 400 Hz; and further includes a crystal-controlled clock source 6H for producing the 3.579 MHz Clock. The output of decoder 6F is connected to the row select bus conductors of the system bus. The four least significant bit positions of latch 6D provide the Card Select Nibble to the system bus. The 8-bit output of latch 6E provides the Command Word to the system bus. The Prompt Tone and the 3.579 Mhz Clock are applied to the system bus. The digitally coded commands that controlling computer 3C issues to sub-system 1C are received in serial form by UART 6A. These digitally coded commands include commands having a two-byte format, one byte defining a card address and another byte defining a Command Word. A card address byte, converted from serial to parallel by UART 6A, undergoes two levels of decoding, one level to address a row of line cards, and another level to address a line card within the addressed row. As to the row-addressing, the most significant nibble of the addressing byte is, after it is latched within part of address latch 6D, decoded by decoder 6F so that only a selected conductor of the eight-conductor row select bus propagates a true signal whereas the remaining conductors propagate a false signal. Because there are seven rows in this embodiment, three addressing bits suffice to identify a row. The most significant bit of a group of eight bits transmitted from controlling computer 3C may be coded to distinguish an address from a Command Word. If, for example, row 0 of the matrix of line cards is being addressed, Row Select 0 (FIG. 5) will be true. In bus controller (0), jumper 5D connects a terminal pair of row address selector C such that the true condition of Row Select 0 causes the output of AND gate 5F to become true (if the row has not been disabled for service via actuation of row service switch 5H). While the output of AND gate 5F is true, decoder 5E is enabled to decode the Card Select Nibble provided by part of latch 6D (FIG. 6). If, for example, line card 3A(0,1) is being addressed, the Card Select Nibble will cause decoder 5E to force the Card Select 1 signal to be true, and to force the Card Select 0 signal and each of Card Select 2 through Card Select 15 signals to be false. The digitally coded status data that controlling computer 3C receives from line connection sub-system 1C are transmitted in serial form by UART 6A. The signal flow in this direction proceeds from a row bus to a tristate bus driver 5B within the corresponding bus controller. The output of AND gate 5F is applied to an enable input of tri-state bus driver 5B to perform the same kind of selection function as has been described above, whereby only one row bus at a time is selected to provide a Status Word to the system bus. UART 6A on communications card 3B serializes the Status Word it receives from the system bus, and transmits it as its serial data output to controlling computer 3C. With reference to FIGS. 7, 8, and 9, there will now be described circuitry included on another system card, viz, monitor card 3F. Monitor card 3F defines, among other things, the interface between line connection sub-system 1C and supervisory station 1I; i.e., monitor phone line 1J has one of its ends connected to monitor card 3F as shown in FIG. 7, and has its opposite end connected to supervisory station 1I. Some of the circuitry shown in FIG. 7, in particular circuitry indicated generally at 7, performs functions for a supervisory connection controller for cooperating with supervisory station 1I to form opposite ends of a call connection path. Other circuitry shown in FIG. 7 performs functions for providing status data to controlling computer 3C. Monitor card 3F includes command-decoding circuitry (shown in FIG. 9) for producing various logic signals, some of which cause logic and sequencing circuitry on monitor card (shown in FIG. 8) to produce other logic signals in a predetermined sequence. As to the decoding circuitry depicted in FIG. 9, it includes three decoders 9A, 9B, and 9C, and a Schmitt trigger driver 9D. The input to driver 9D is a Card Select signal received from row bus (1). As indicated by FIGS. 2 and 3, monitor card 3F occupies the system slot of row 1 of sub-system 1C. When the bus controller for row 1 is enabled and its decoder 5E (FIG. 5) forces the Card Select 0 signal to be true, circuit 9D enables decoders 9A, 9B, and 9C to produce a valid decoded output in response to the Command Word being propagated to monitor card 3F from controlling computer 3C via the system bus, Schmitt trigger drivers 5A (FIG. 5), and row bus (1). The circuitry depicted in FIG. 9 also includes a Schmitt trigger driver circuit 9E and a Schmitt trigger driver circuit 9F. Circuit 9E provides for buffering the 3.579 MHz clock. Circuit 9F provides for buffering a Message 2 Start/Stop Strobe. As shown in FIG. 7, circuitry 7 of the supervisory station connection controller includes an incoming transient-surge suppressor 7A connected across monitor phone line 1J, Tip and Ring lines, and a diode bridge 7B connected between monitor phone line 1J and the Tip and Ring lines to ensure correct polarity for DC potential of the Tip line relative to the Ring line. Circuitry 7 further includes a transformer 7C having a capacitor 7D connected in parallel with its primary winding, a zener diode 7E, a hook switch simulating controllable switch 7F, which is a relay. While switch 7F is closed and DC loop current flows through it, such DC loop current flows from the Tip line, through the primary winding of transformer 7C, through zener diode 7E, through the closed switch 7F, to the Ring line. While such loop current flows, a voltage is developed across zener diode 7E. A loop-current detecting circuit 7G is connected to be responsive to the voltage developed across zener diode 7E, and includes a switching transistor that is on only while loop current is flowing. Circuitry 7 further includes a ground-start simulating controllable switch 7H that, like hook switch simulating controllable switch 7F, is a relay. Circuitry 7 further provides for sensing and detecting a ringing signal. In particular, a ringing-signal detecting circuit 7I has its input AC coupled across the Tip and Ring lines, and has a switching transistor that is on if a ringing signal is present. The controllable switches of circuitry 7 operate in accord with logic signals, the values of which are determined by commands that are issued by controlling computer 3C. One of the logic signals produced by the sequencing circuitry depicted in FIG. 8 is identified in FIG. 8 as "CTL 90-Line Connect Control." This CTL 90 signal is applied as the control input to hook switch simulating switch 7F shown in FIG. 7, as indicated by the reference to "CTL 90-Line Connect Control" adjacent the line leading to switch 7F. The foregoing is in accord with a notational convention used generally throughout the drawings to indicate how various circuits on separate drawing figures are interconnected. Also, as part of the notational convention, the terms "Control," "Strobe," and "Status Bit," are used to indicate the nature of a signal. The term "Control" applies to a signal that has either a true value to establish a control condition or a false value to establish an opposite control condition. The term "Strobe," applies to a signal having a pulse format for initiating or terminating an operation. The term "Status Bit" applies to a signal containing information to be provided to controlling computer 3C is a part of a group defining a Status Word. Further with respect to logic signal notation, the circuitry shown throughout the drawings uses "positive logic control." For example, a true logic level for the CTL 90 control signal causes the switch it controls, viz, switch 7F, to close; otherwise the switch 7F is open. In addition to the Line Connect Control signal (CTL 90) described above, a Ground Line Control signal (CTL 86) is produced by the sequencing circuitry depicted in FIG. 8 and used to control circuitry 7. More particularly, this CTL 86 signal is used to control ground start simulating switch 7H. A CK signal (CTL 80) is a buffered clock signal provided by driver 9E (FIG. 9), and is applied as a trigger input to each of two retriggerable one-shots 7J and 7K. One-shot 7J responds to loop-current detecting circuit 7G to produce a Line Current Status Bit signal (STA 8). One-shot 7K responds to ringing-signal detecting circuit 7I to produce a Ring Detect Status signal (STA 9). The secondary winding of transformer 7C is connected to a controllable switch 7L that defines a controllable inter-connection means arranged between the connection controller circuitry 7 and a conductor of the Audio Bus used for propagating a Monitor Audio Signal (AUD 4). Controllable switch 7L is a field effect transistor (FET); a suitable alternative is a relay. Controllable switch 7L is closed while an Audio Connect Control signal (CTL 91) is true; otherwise it is open. The logic level of the Audio Connect Control signal is determined by circuitry depicted in FIG. 8 in accord with signals produced by the command-decoding circuitry shown in FIG. 9. A circuit node is defined where controllable switch 7L and the secondary winding of transformer 7C are interconnected. Four other controllable switches 7M, 7N, 7O, and 7P are also connected to that circuit node. In operation of system 1A, no more than one of these four switches is closed at any one time. During the time that a call is being placed to a remote supervisor, switch 7M is closed, and the output of a DTMF generator 7Q is coupled through switch 7M so as to dial a telephone number at which the remote supervisor can be reached. Before such dialing commences, a sequence of operations is performed, under control of controlling computer 3C; the sequence includes loading DTMF generator 7Q with a selected telephone number, closing switch 7F to simulate an off hook condition, operating switch 7H in accord with conventional ground start line protocol so that dial tone will be requested, and then causing DTMF generator 7Q to output the stored telephone number for the supervisor. Switches 7N, 7O, and 7P provide switching control for propagating, respectively, Message 1 Audio (AUD 6), Message 2 Audio (AUD 7), and Message 3 Audio (AUD 8). These three audio signals are used in the automatic message transmitting feature. A DTMF receiver 7R has its input capacitively connected to the above-mentioned node to which the foregoing numerous switches are connected; receiver 7R provides for detection of in-band signals used in the operation of system 1A. A decoder 7S responds to the parallel output signal of receiver 7R to produce eight different strobe signals that are identified in FIG. 7. The circuitry depicted in FIG. 7 further includes circuitry for defining the information content of a Status Word to be provided to controlling computer 3C regarding conditions of operation of monitor card 3F. This circuitry includes a three-stage bus driver and multiplexer 7T, and a three-stage, four-bit latch 7U. Multiplexer 7T has an "A Enable" control input and a "B Enable" control input that receive, respectively, a Status A Control signal (CTL 78) and a Status B Control signal (CTL 77). These control signal are produced by decoder 9C (FIG. 9) in response to digitally coded commands issued by controlling computer 3C. When controlling computer 3C issues a digitally coded command to obtain Status A data from monitor card 3F, decoder 9C forces the Status A Control signal (CTL 78) to be true. In response, multiplexer 7T propagates signals from its "A" data inputs to Bits 4-7 of the Status Word. Its "A" inputs include Ground Return, i.e., a false logic value; the Audio Connect Control signal (CTL 91); an On-Hook Timer Status Bit signal (STA 10); and the Line Current Status Bit signal (STA 8). When controlling computer 3C issues a digitally coded command to obtain Status B data from monitor card 3F, decoder 9C forces the Status B Control signal (CTL 77) to be true. In response, multiplexer 7T propagates signals from its "B" data inputs to Bits 4-7 of the Status Word. Its "B" inputs include Ground Return; the Line Connect Control signal (CTL 90); and the Ring Detect Status signal (STA 9). One of the "B" inputs is a spare. As for Bits 0-3 of a status word provided by monitor card 3F, latch 7U has an enable input that responds to the Status A Control signal (CTL 78). When controlling computer 3C issues a digitally coded command to obtain Status A data from monitor card 3F, decoder 9C forces the Status A Control signal (CTL 78) to be true. In response, latch 7U propagates signals from its data inputs to Bits 0-3 of the Status Word. Its data inputs are the four parallel output signals of receiver 7R, i.e., the CTL 82, CTL 83, CTL 84, and CTL 85 signals. Latch 7U copies these signals whenever receiver 7R forces a DTMF Data Valid Control signal (CTL 81) to become true. With reference to FIG. 8, the circuitry depicted therein is generally related to sequencing functions, a representative example of which has been generally described above concerning the sequence of operations involved in going off-hook and dialing the supervisor. The circuitry of FIG. 8 includes a busy line flip flop 8A that, like other flip flops and other bit-storing devices described below, has a Q output and a Q output. In the case of flip flop 8A, only the Q output is connected to other circuitry. While flip flop 8A is in its set state, its Q output produces a true logic level signal, and its Q output produces a false logic level signal. While in its reset state, its Q output is false and its Q output is true. Flip flop 8A is set by a Busy Line Control signal (CTL 60), and is reset by an Un-Busy Line Control signal (CTL 59). These setting and resetting signals are produced by decoder 9A (FIG. 9) in response to digitally coded commands issued by controlling computer 3C. The Q output of flip flop 8A is connected to one input of a two-input OR gate 8B, the output of which produces the Ground Line Control signal (CTL 86) for controlling ground start simulating switch 7H (FIG. 7). The circuitry of FIG. 8 further includes a gate 8C that produces a signal to set a phone line flip flop 8D if an Off-Hook And Dial Control signal (CTL 57) is true and an On-Hook Timer Status Bit signal (STA 10) is false. The Off-Hook And Dial Control signal is produced by decoder 9A (FIG. 9) in response to digitally coded commands issued by controlling computer 3C. The On-Hook Timer Status Bit signal is produced by an on-hook timer circuit 8E. Phone line flip flop 8D is reset when the output of an OR gate 8F is true; this occurs if either an On-Hook Control signal (CTL 58) or an Activate Timer End Strobe signal (STB 23) becomes true. The On-Hook Control signal is produced by the decoder 9A (FIG. 9) in response to digitally coded commands issued by controlling computer 3C. The Activate Timer End Strobe signal is produced by a timer-end one-shot circuit 8G. The circuitry of FIG. 8 further includes a disconnect timer circuit 8H that has a trigger input and a clear input. When triggered, disconnect timer 8H initiates a sequence of operations involved in playing a message (message 2) to the supervisor and then terminating the call connection path between supervisory station 1I and monitor card 3F. Message 2 in this embodiment has a duration of approximately ten seconds, and is cyclically generated. To ensure that the full message is played from start to finish, disconnect timer circuit 8H provides a timing interval having a maximum duration of twice the length of the message, i.e., twenty seconds. The trigger input of disconnect timer circuit 8H is connected to the Q output of flip flop 8D. A false-to-true transition in the signal produced by the Q output of flip flop 8D, triggers disconnect timer circuit 8H to start to define its timing interval. During this timing interval the Q output of disconnect timer 8H is true. This forces the output signal of an OR gate 8I to remain true; it had been true because the signal produced by the Q output of flip flop 8D had been true until disconnect timer 8H was triggered. The output signal of OR gate 8I is the Line Connect Control signal (CTL 90) that controls hook-switch simulating switch 7F (FIG. 7). Thus, hook switch 7F continues to simulate an off-hook condition while the timing interval defined by disconnect timer 8H is in progress. Also while the signal produced by timer circuit 8H is true, a message 2 flip flop 8J is enabled to respond to the Message 2 Start/Stop Strobe signal (STB 13) which is applied to its toggle input. When the STB 13 strobe occurs while the signal produced by disconnect timer 8H is true, message 2 flip flop 8J changes state. The output signal it produces, a Message 2 Control signal (CTL 89), controls switch 7O (FIG. 7) so that a Message 2 Audio signal (AUD 7) is gated through by the supervisory station connection controller circuitry 7. Thus, this CTL 89 signal becomes true only at the start of a given cycle of message 2, and only if disconnect timer 8H has initiated the sequence of operations for terminating the call connection path between supervisory station 1I and monitor card 3F. The true-to-false transition in the signal produced by OR gate 8I triggers on-hook timer 8E. The timing interval provided by on-hook timer 8E is suitably two seconds; this duration is sufficiently long as to prevent any ambiguity with a "hook flash" type operation of a momentary on-hook condition. The circuitry of FIG. 8 further includes a group of sequencing circuits arranged in tandem between phone line flip flop 8D and timer end one-shot 8G. These circuits include dial tone one-shot 8K, delay one-shot 8L, dial one-shot 8M, and activate timer 8N. The output of dial tone one-shot 8K is connected to one of the inputs of OR gate 8B. Thus, while the signal produced by one-shot 8K is true, it forces the Ground Line Control signal (CTL 86) to be true. This in turn causes ground-start simulating switch 7H (FIG. 7) to close temporarily, so as to stimulate the source of dial tone to provide it before automatic dialing commences. Suitably, dial tone one-shot defines a 0.5 second pulse for this purpose. Delay one-shot 8L is triggered by the true-to-false transition in the pulse signal produced by dial tone one-shot 8K and defines a delay period sufficiently long to allow for the source of dial tone to react and to provide the dial tone. Suitably, this delay period is one second. The true-to-false transition in the signal produced by delay one-shot 8L triggers dial one-shot 8M to force a DTMF Dial Control signal (CTL 87) to become true. This CTL 87 signal is coupled through diodes to R.sub.4 and C.sub.1 inputs of DTMF generator 7Q. These inputs in combination correspond to the "#" symbol; the parallel signals coupled through the diodes initiate the dialing. This CTL 87 signal also controls switch 7M (FIG. 7) so that the automatic telephone number dialing output signal of DTMF generator 7Q is gated through by the supervisory station connection controller circuitry 7. Suitably, the timing interval defined by dial one-shot 8M is two seconds. This is long enough for as many as twenty-one digits to be produced as the telephone number to be dialled to reach supervisory station 1I. The true-to-false transition in the CTL 87 signal triggers activate timer circuit 8N to start defining a verification timing interval, preferably having a maximum duration of 30 seconds. The Q output of activate timer 8N produces a Message 1 Control signal (CTL 88). This CTL 88 signal controls switch 7N (FIG. 7) to provide for selectively gating Message 1 Audio (AUD 6) for transmission by the system. When an supervisor answers the call at the called supervisory station, the transmission of Message 1 Audio alerts the supervisor that the call has been originated by the system, and provides a prompt for entry of a code defining the security clearance signal. Activate timer circuit 8N has a clear input that responds to a DTMF Strobe 0 Key Strobe Signal (STB 20). This strobe signal is produced by decoder 7S (FIG. 7) in response to detection of an in-band signal by DTMF receiver 7R; this strobe signal is normally false, and defines a true pulse if a security-clearance signal is provided. This strobe signal is also applied to a disable input of an activate abort one-shot 8O which has its trigger input connected to the Q output of activate timer circuit 8N and which produces a System Initialize Strobe signal (STB 30). If the security verification signal is provided within the maximum time allotted by timer circuit 8N, then the STB 20 signal clears timer circuit 8N and at the same time disables one-shot 8O from being triggered. If timer circuit 8N completes timing out the maximum time it allots, then the true-to-false transition in the signal it provides on its Q output triggers one-shot 8O, thereby causing a true pulse to be defined in the STB 30 signal. The occurrence of a true pulse in the STB 30 signal, in effect, aborts this sequence of events involved in placing a call to a supervisor. It does so by resetting all timers, one-shots, and flip flops on monitor card 3F. This same resetting function is subject to software control. That is, controlling computer 3C issues a command for monitor card 3F to perform this resetting function; this command causes decoder 9A (FIG. 9) to force the System Initialization Control signal (CTL 56) true. Further as to software control, controlling computer 3C, as will be explained below, provides for counting the number of tries to place such a call and causes automatic retries up to a maximum number of retries. The maximum number of retries can be set as desired from supervisory computer 3D. The circuitry of FIG. 8 further includes an AND gate 8P, an audio connect flip flop 8Q, an OR gate 8R, and a message 3 flip flop 8S. AND gate 8P produces a signal to control the clear input of disconnect timer 8H, in response to two signals, viz, the STB 13 signal and the CTL 89 signal. Audio connect flip flop 8Q has a set input that responds to an Audio On Control signal (CTL 68) produced by decoder 9B (FIG. 9) in response to digitally coded commands issued by controlling computer 3C. The Q output of flip flop 8Q produces the Audio Connect Control signal (CTL 91) that controls inter-connection switch 7L (FIG. 7). As to OR gate 8R, the signal it produces is applied to the reset input of flip flop 8Q; this signal is true if and only if any one of four signals applied to OR gate 8R is true. One of these four signals is an Audio Off Control signal (CTL 69) that is produced by decoder 9B (FIG. 9) in response to digitally coded commands issued by controlling computer 3C. Another of these four signals is the Message 1 Control signal (CTL 88) produced by activate timer 8N. Another of these four signals is the Message 2 Control signal (CTL 89) produced by message 2 flip flop 8J. Another of these four signals is the Message 3 Control signal (CTL 92) produced by message 3 flip flop 8S. As to Message 3 flip flop 8S, its state is controlled by signals (CTL 61 and CTL 62) that are produced by decoder 9A (FIG. 9) in response to digitally coded commands issued by controlling computer 3C. Message 3 flip flop 8S produces the CTL 92 signal that controls switch 7P (FIG. 7) to provide for selectively gating Message 3 Audio (AUD 8) for transmission by the system. With reference to FIGS. 10-13, there will now be described circuitry included on audio message card 3G which occupies the system slot within row 2 of line connection sub-system 1C. The functions audio message card 3G performs relate to generation of the four messages that system 1A automatically transmits at selected times. (Three of these messages apply equally to a supervisor or to any attendant; one of them applies specifically to an attendant at the end of a shift.) To perform these functions, audio message card 3G cooperates with controlling computer 3C via row bus (2), the system bus, and communications card 3B to receive digitally coded commands and to provide status data. The circuitry on audio message card 3G for decoding digitally coded commands is shown in FIG. 12. The circuitry on audio message card 3G for applying status data to the status bus is shown in FIG. 13. Three of the messages that system 1A automatically generates and transmits are generated by three identical circuit arrangements. FIG. 10 shows such a circuit arrangement, and sets out references in general terms such as "Channel i." It should be understood that this circuit arrangement is replicated three times such that there are in the preferred embodiment a Channel 1, a Channel 2, and a Channel 3. Another message, viz, Message 4, is generated by a circuit arrangement, shown in FIG. 11, that, in most respects except those specifically described, is identical to the circuit arrangement of FIG. 10. The circuitry shown in FIG. 10 includes an audio connect flip flop 10A, a switch 10B controlled by flip flop 10A, and a speech processor 10C. In the preferred embodiment, speech processor 10C is an OKI 6258 Solid State Recorder Speech Processor integrated circuit chip. It handles analog-to-digital and digital-to-analog conversion, and operates in cooperation with a crystal 10D, tuned to 4 MHz in this embodiment. It has numerous outputs, including a "DA OUT" output and a "V Clock" output which are connected to a low pass filter 10E. A buffer amplifier is connected between the output of low pass filter 10E and switch 10B. Another output of speech processor 10C is "Play Mon"; the signal that it produces is a Play-Back Status Bit. This signal is buffered and applied to an LED 10F. This and two other LED's shown in FIG. 10 are mounted on the audio message card 3G so as to provide an indication to maintenance personnel for use in servicing the system. Another output of speech processor 10C is "Rec Mon"; the signal it produces is a Record Status Bit. Another output is "OVF(FST)"; the signal it produces is an Overload Status Bit. Another set of outputs of speech processor 10C are connected to a 19-conductor address bus used to propagate addressing signals to a message memory array generally indicated at 10G. Eight ROM chips are arranged in parallel to define this message memory array. One at a time of these eight ROM chips is selected by a one-out-of-eight select signal produced by a decoder 10H. The selected ROM chip responds to the addressing signal provided by speech processor 10C to apply an eight bit byte to a data bus connecting the output to the ROM chips to a data input of speech processor 10C. Decoder 10H decodes a three-bit wide signal produced by a latch 10I. The input signals applied to latch 10I are three parallel bits supplied as part of a command word issued by controlling computer 3C, and a control signal for latch control which is produced by command-decoding circuitry shown in FIG. 12. Speech processor 10C receives three control signals directly from the command-decoding circuitry of FIG. 12; these are an All Clear Control signal, a Flag Reset Control signal, and a Pause Control signal. Speech processor 10C receives another control signal from the output of an OR gate 10J which responds to a Start/Stop Control signal and a Restart Strobe signal. The Start/Stop Control signal is produced by the command-decoding circuitry shown in FIG. 12. The Restart Strobe signal is produced by a one-shot 10K that is triggered by a signal produced by one-shot 10L. As stated above, the circuitry shown in FIG. 10 represents one of three circuit arrangements having identical construction for handling a respective one of three messages the system automatically generates and transmits. The following cross-reference table provides information about how the command-decoding circuitry of FIG. 12 is interconnected to these three circuit arrangements, which are referred to in the table as Channel 1, Channel 2, and Channel 3. ______________________________________ Cross-Reference Table Regarding Channel 1, Channel 2, and Channel 3 Signals Signal Channel CTL or STB No. ______________________________________ Audio Connect Control 1 CTL 98 Audio Connect Control 2 CTL 106 Audio Connect Control 3 CTL 114 Audio Disconnect Control 1 CTL 99 Audio Disconnect Control 2 CTL 107 Audio Disconnect Control 3 CTL 115 All Clear Control 1 CTL 94 All Clear Control 2 CTL 102 All Clear Control 3 CTL 110 Flag Reset Control l CTL 95 Flag Reset Control 2 CTL 103 Flag Reset Control 3 CTL 111 Pause Control 1 CTL 96 Pause Control 2 CTL 104 Pause Control 3 CTL 112 Start/Stop Control l CTL 97 Start/Stop Control 2 CTL 105 Start/Stop Control 3 CTL 113 Restart Strobe l STB 24 Restart Strobe 2 STB 25 Restart Strobe 3 STB 27 Latch Control 1 CTL 130 Latch Control 2 CTL 131 Latch Control 3 CTL 132 ROM 0 Select Control 1 CTL 134 ROM 0 Select Control 2 CTL 145 ROM 0 Select Control 3 CTL 156 ROM l Select Control l CTL 135 ROM 1 Select Control 2 CTL 146 ROM 1 Select Control 3 CTL 157 ROM 2 Select Control 1 CTL 136 ROM 2 Select Control 2 CTL 147 ROM 2 Select Control 3 CTL 158 ROM 3 Select Control 1 CTL 137 ROM 3 Select Control 2 CTL 148 ROM 3 Select Control 3 CTL 159 ROM 4 Select Control 1 CTL 138 ROM 4 Select Control 2 CTL 149 ROM 4 Select Control 3 CTL 160 ROM 5 Select Control 1 CTL 139 ROM 5 Select Control 2 CTL 150 ROM 5 Select Control 3 CTL 161 ROM 6 Select Control 1 CTL 140 ROM 6 Select Control 2 CTL 151 ROM 6 Select Control 3 CTL 162 ROM 7 Select Control 1 CTL 141 ROM 7 Select Control 2 CTL 152 ROM 7 Select Control 3 CTL 163 Message Audio 1 AUD 6 Message Audio 2 AUD 7 Message Audio 3 AUD 8 Start/Stop Strobe l STB 23 Start/Stop Strobe 2 STB 13 Start/Stop Strobe 3 STB 26 Restart Strobe 1 STB 24 Restart Strobe 2 STB 25 Restart Strobe 3 STB 27 Play Back Status Bit 1 STA 11 Play Back Status Bit 2 STA 14 Play Back Status Bit 3 STA 17 Record Status Bit 1 STA 12 Record Status Bit 2 STA 15 Record Status Bit 3 STA 18 Overload Status Bit 1 STA 13 Overload Status Bit 2 STA 16 Overload Status Bit 3 STA 19 Memory Select Control Bit 0 l CTL 142 Memory Select Control Bit 0 2 CTL 153 Memory Select Control Bit 0 3 CTL 164 Memory Select Control Bit 1 1 CTL 143 Memory Select Control Bit 1 2 CTL 154 Memory Select Control Bit 1 3 CTL 165 Memory Select Control Bit 2 l CTL 144 Memory Select Control Bit 2 2 CTL 155 Memory Select Control Bit 2 3 CTL 166 ______________________________________ As to the fourth kind of message that the system automatically generates and transmits, reference is made to FIG. 11. The reference numbers used in FIG. 11 are correlated with those used in FIG. 10 so as to indicate circuit elements that are identical. For example, audio connect flip flop 11A (FIG. 11) has the same construction and operation as audio connect flip flop 10A (FIG. 10). The circuitry of FIG. 11 differs from that of FIG. 10 in the following respects. First, message memory array 11G includes a RAM; i.e., it is written into as well as read from during normal operation of the system in contrast to the all-ROM configuration of message memory array 10G (FIG. 10). Second, additional outputs of speech processor 11C are used in the circuit arrangement of FIG. 11; these are the CAS and RAS outputs that are connected to corresponding inputs of a four megabyte RAM chip 11M of message memory array 11G. Third, three of the inputs in speech processor 11C, viz, the CA1, CA2, and CA3 inputs, are connected differently. In particular, the CA1 input is connected to the Q.sub.2 output of latch 11I (this being the most significant bit of the three bit positions of the latch); the CA2 input is connected to the output of an AND gate 11N, and the CA3 input is connected to the output of an AND gate 11O. AND gate 11N has two inputs, one connected to the most significant of these three bit positions (Q.sub.2), and the other connected to the next most significant bit position (Q.sub.1). AND gate 11O has two inputs, one connected to the most significant of these bit positions (Q.sub.2), and the other connected to the least significant bit position (Q.sub.0). The remaining differences involve additional circuits for switchably applying an audio signal to speech processor 11C so that such audio signal can be digitized and stored in the message memory array 11G. The additional circuits are an audio connect flip flop 11P, a switch 11Q controlled by flip flop 11P, a buffer amplifier 11R through which the audio signal propagates to switch 11Q and, while switch 11Q is closed, through a low pass filter 11S to an input of speech processor 11C. With reference to FIG. 12, the command-decoding circuitry for audio monitor card includes four decoder circuits 12A, 12B, 12C, and 12D, each of which is enabled by a pair of enabling signals to decode Bits 0-3 of the command word received via the command word bus portion of the system bus. One of the enabling signals is produced by a Schmitt trigger driver circuit 12E that responds to the Card Select signal. Another decoding circuit 12F provides four enabling signals, one for each decoder 12A-12D. Decoder 12F, while enabled by the Card Select signal, decodes Bits 4-6 of the command word. With reference to FIG. 13, the circuitry shown therein provides for communicating status data from audio message card 3G to the status bus so that the status data can propagate to controlling computer 3C. This circuitry includes four tri-state bus drivers 13A, 13B, 13C, and 13D. Having completed the description of the construction of the various circuit arrangements of the three system cards, there will now be described, with reference to FIGS. 14-22, the construction of a line card. As stated above, this specific embodiment of the present invention has 105 line cards, every one of which has the same construction. This modular arrangement is advantageous in numerous respects, particularly for flexibility in configuring a system. Any one of the line cards can be removed from the rack that houses line connection sub-system 1C, for maintenance or the like without necessitating a system shut down. Further, the modular arrangement is advantageous with respect to system expansion; as indicated above, a variety of provisions have been made to facilitate any such system expansion. This modular architecture is further advantageous in that each line card defines a module having its own hardware sequencing circuitry such that a sufficient number of sequencing functions are controlled at the line card level to provide for autonomous operation of call extending operations. Thus, even if a power failure or other untoward event interrupts the operation of controlling computer 3C during a peak period of incoming traffic, each line card can continue to operate to extend a sequence of incoming calls. To provide an introduction to the construction of a line card, there will now be described the functional block diagram of FIG. 14. The Tip andrrrr Ring lines of an incoming phone line are connected to an incoming line connection controller 14A. To ensure a sufficient power level for audio signals propagated by the phone lines, each such incoming phone line is suitably connected to the output of a conventional voice frequency repeater VFR (not shown). FIG. 14 also shows the Tip and Ring lines of an outgoing phone line and an outgoing line connection controller 14B that is connected to the outgoing phone line. An audio selector inter-connection switch 14C is arranged between controllers 14A and 14B. (Circuitry for line connection controllers 14A and 14B and circuitry for inter-connection switch 14C are shown in FIG. 15.) Switch 14C is connected to a row bus interface which includes an audio interface 14D, a decoder for commands and special function inputs 14E, and a tri-state bus driver 14F. (Circuitry for audio interface 14D is shown in FIG. 16. Command-decoding circuitry 14E is shown in FIG. 21. Tri-state bus driver circuitry 14F for providing status data is shown in FIG. 22.) FIG. 14 indicates, beneath the row bus interface, lines labeled "Audio I/O" and "Digital I/O For Command And Status" which connect to the row bus. FIG. 14 shows, above the row bus interface, lines connecting the row bus interface to each of the remaining functional blocks of the line card. These include, in addition to blocks 14A-14C mentioned above, a traffic mode controller 14G, a DTMF number generator and register 14H, and in-band signal decoder and source discriminator 14I, and a broadcast mode controller 14J. (Circuitry that performs functions of traffic mode controller 14G is shown in FIG. 19. Circuitry for DTMF generation and decoding is shown in FIG. 20.) With reference to FIG. 15, there will now be described circuitry for implementing connection controllers 14A and 14B and inter-connection switch 14C. Circuitry generally indicated at 14A in FIG. 15 performs functions for a station connection controller for cooperating with an originating station to form opposite ends of a call connection path. This circuitry is implemented by the same components arranged in the same way as the circuitry for supervisory station connection controller 7 (FIG. 7). Circuitry generally indicated at 14B in FIG. 15 performs functions for a station connection controller for cooperating with a multi-purpose station to form opposite ends of a call connection path. This circuitry is also implemented by the same components arranged in the same way as the circuitry for the above-mentioned station connection controllers. Inter-connection switch 14C is implemented by a FET switch just as switch 7L (FIG. 7) is, within monitor card 3F. As to controller 14A, it includes controllable switches and circuitry for producing signals representing conditions of operation of controller 14A. The controllable switches are an incoming line ground-start simulating switch 15A, and an incoming line hook-switch simulating switch 15B. The circuitry of controller 14A for producing the condition-representing signals includes a one-shot 15C, and two retriggerable one-shots 15D and 15E. One-shot 15D produces an Incoming Line Current Status Bit signal (STA 2), and is responsive to a current detect circuit that is connected in the same way that circuit 7G (FIG. 7) is connected within the supervisory station connection controller 7. Thus, the STA 2 status bit signal it produces is true while opposite ends of a call connection path are completed; in other words, an originating party is off-hook and hook switch simulating switch 15B is simulating an off-hook condition. One-shot 15E produces an Incoming Line Ring Detect Status Bit signal (STA 3). One-shot 15E is responsive to a ring detect circuit that is connected in the same way that circuit 7I (FIG. 7) is connected within the supervisory station connection controller 7. Thus, the STA 3 status bit signal it produces is true while a ring signal is being detected. One-shot 15C produces an Incoming Line Current Termination Strobe signal (STB 0), and is triggered by the STA 2 status bit signal produced by one-shot 15D. As to the controller 14B, it includes controllable switches and circuitry for producing signals representing conditions of operation of controller 14B. The controllable switches are an outgoing line hook-switch simulating switch 15F, and an outgoing line ground-start simulating switch 15G. The circuitry of controller 14B for producing the condition-representing signals includes two retriggerable one-shots 15H and 15I. One-shot 15H produces an Outgoing Line Ring Detect Status Bit signal (STA 0), and is responsive to a ring detect circuit that is connected in the same way that circuit 7I (FIG. 7) is connected within the supervisory station connection controller 7. Thus, the STA 0 status bit signal it produces is true while a ring signal is being detected. One-shot 15I produces an Outgoing Line Current Status Bit signal (STA 1), and is responsive to a current detect circuit that is connected in the same way that circuit 7G (FIG. 7) is connected within the supervisory station connection controller 7. Thus, the STA 1 status bit signal it produces is true while opposite ends of a call connection path are completed; in other words, a called party such as an attendant is off-hook and hook switch simulating switch 15B is simulating an off-hook condition. As to inter-connection switch 14C, it is connected between controller 14A and 14B. One end of switch 14C is also connected to a conductor used to propagate an Incoming Line Audio signal (AUD 1). The opposite end of switch 14C is connected to a conductor used to propagate an Outgoing Line Audio signal (AUD 0). With reference to FIG. 16, there will now be described circuitry for implementing an audio interface incorporating audio selection switches. This circuitry includes eleven controllable switches 16A-16K, each of which is preferably implemented by a FET. Each of switches 16A-16C has one end connected to the conductor used to propagate the Incoming Line Audio signal (AUD 1). As indicated by the arrangement of controllable switches 16A-16C, the Incoming Line Audio signal (AUD 1) can be any one of three signals depending upon which one, if any, of switches 16A-16C is closed. The Incoming Line Audio signal (AUD 1) will be the Message 4 Audio signal (AUD 9) if switch 16A is closed; the Music Audio signal (AUD 5) if switch 16B is closed; the Monitor Audio signal (AUD 4) if switch 16C is closed. Each of switches 16D-16K has one end connected to the conductor used to propagate the Outgoing Line Audio signal (AUD 0). As indicated by the arrangement of controllable switches 16D-16K, the Outgoing Line Audio signal (AUD 0) can be any one of eight signals depending upon which one, if any, of switches 16D-16K is closed. The Outgoing Line Audio signal (AUD 0) will be the Monitor Audio signal (AUD 4) if switch 16D is closed; the Music Audio signal (AUD 5) if switch 16E is closed; the Message 4 Audio signal (AUD 9) if switch 16F is closed; the Message 3 Audio signal (AUD 8) if switch 16G is closed; the Message 2 Audio signal (AUD 7) if switch 16H is closed; the Message 1 Audio signal (AUD 6) if switch 16I is closed; the Prompt Tone Audio (AUD 3) if switch 16J is closed; the DTMF Dial Audio signal (AUD 2) if switch 16K is closed. Resistors are indicated in FIG. 16 in series with individual controllable switches; these resistors provide for individually adjusting the sound level of each of the various audio signals and, therefore, implement the audio interface function indicated in block 14D (FIG. 14). With reference to FIG. 17, there will now be described circuitry for controlling the audio selection switches. This circuitry includes a monitor flip flop 17A and a monitor side flip flop 17B, which perform functions involved in selectively propagating audio signals between the particular line card and supervisory station 1I. Flip flop 17A produces the Monitor Status signal (STA 6). An audio connect flip flop 17C produces the Audio Connect Control signal (CTL 44) that controls inter-connection switch 14C. Audio connect flip flop 17C is set by a signal produced by an OR gate 17D and is reset by a signal produced by an OR gate 17E. A message 4 flip flop 17F produces a signal that is switched through an option switch 17G. Depending upon the setting of 17G, one of two signals is maintained at the false logical level by virtue of a resistor and the other of the two signals is the same as the signal produced by Message 4 flip flop 17F. One of these two signals is an Outgoing Line Message 4 Control signal (CTL 45) that controls switch 16F (FIG. 16). The other of these two signals is an Incoming Line Message 4 Control signal (CTL 46) that controls switch 16A (FIG. 16). A message 3 flip flop 17H is set by a signal produced by an OR gate 17I, and is reset by a signal produced by an OR gate 17J, and produces a Message 3 Control signal (CTL 47) which, when true, causes switch 16G (FIG. 16) to close to propagate the Message 3 Audio signal (AUD 8) as the Outgoing Line Audio signal (AUD 0). To provide an option whether, when a caller hangs up, to play message 3 audio to the attendant, an option jumper controls whether the STB 0 signal, which is produced by one-shot 15E (FIG. 15), is |