TELEPHONE LINE COMMUNICATIONS CONTROL SYSTEM

Abstract: The present invention is a telecommunications control system for accepting a plurality of multi-purpose stations for use as attendant stations (1D-1) in an attendant service complex to service calls directed to the system from originating stations (1B-1). This system comprises a line connection sub-system (1C) having a first plurality of connection controllers. Each connection controller in this first plurality of connection controllers provides for cooperating with a respective one of the 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. The line connection sub-system further includes a second plurality of connection controllers. Each connection controller in this second plurality of connection controllers provides for cooperation with a respective one of the plurality of originating stations in defining opposite ends of a call connection path. A controllable interconnection is arranged between the first and second plurality of connection controllers and includes a system for controlling the interconnection system such that incoming calls from originating stations are extended to multi-purpose stations that have been accepted as attendant stations. Control of the interconnection system is accomplished by a computer processing sub-system (1E) which includes provisions for supervision of the system from a supervisory console (1K).

Description: TELEPHONE LINE COMMUNICATIONS CONTROL SYSTEM Background of the Invention This invention relates to telephone communicatio control systems. Many organizations gather and distribute informati in the course of telephone calls serviced at least in pa by members of a staff of attendants. Such organizatio include major corporations which conduct television other media advertising campaigns to encourage custome and potential customers to call the organization via telephone number that is toll-free to the caller. T area code "800" is used in the United States for su toll-free telephone numbers. As for gathering and distribu ing information, this typically entails having a servi attendant elicit the caller's name and address and so kind of ordering information for goods or services a then provide information such as price and delivery inform tion. In some of the many varied situations, the organiz tion is providing "help" to a customer concerning use the organization's goods or services, including goods su as retail computer programs and services such as repair maintenance services under a warranty. Other such organizations include non-commerci public broadcasting stations which solicit contributio from the viewing public to defray the cost of providi the broadcast services. Typically, such stations recei 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 overhea time, such as time spent in completing a connection betwee an incoming line allocated to a call request and a line t 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. Patent No. 3,859,473 to Brown et al. , titled "Centralized Attendant Service Arrange- ment for PABX Complex." An object of the system Brown e al. disclose is to provide a centralized attendant service (CAS) arrangement which permits all incoming calls to 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. Patent No. 3,881,060 to Connell et al., titled "Emergency Reporting System." The system Connell et al. disclose is directe 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 qf 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 securit against use of any of the multi-purpose stations withi the attendant service complex by an unauthorized person. The security-providing means includes means for controllin the switching means to open the call connection path an release the multi-purpose station. This system furthe includes a second plurality of connection controllers. Each connection controller in this second plurality o connection controllers provides for cooperating with respective one of a plurality of originating stations i defining opposite ends of a call connection path. Thi system further includes controllable inter-connectio means arranged between the first and second plurality o connection controllers, and includes means for controllin the inter-connection means such that incoming calls fro originating stations are extended to multi-purpose station 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 par¬ ticularly 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 inσlude 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 connec¬ tion 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. Controll- able 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 incomin call after another to an attendant station with minimu interruption. In a system such as the preferred embodimen of this invention where the networked multi-purpose stations can be at any location serviced by the public switchin network, a relatively large amount of time is required t carry out a call connection operation. An amount of tim in the order of 10 seconds or more is quite significant i 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 substan¬ tially 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 diagra of a system embodying preferred features of the inventio to provide for interactively supervising a co puter-con trolled sub-system to allocate tasks in a network fo servicing incoming calls; FIG. 2 is an annotated map indicating a representa tive, geographically-dispersed configuration of a syste embodying a preferred feature of the invention whereby th public switched network is used to extend calls to multi purpose stations located in various parts of the Unite States; FIG. 3 is a functional block diagram illustrating modular organization of electronic equipment incorporate in the preferred embodiment; FIG. 4 shows mechanical features of the modula organizatio ; FIG. 5 is a block and schematic diagram of a bus controller incorporated in each of a series of rows of line connection sub-system rack mounted in a cabinet i the preferred embodiment; FIG. 6 is a block and schematic diagram of circuitr included on a communications card used in the preferre embodiment; FIG.- 7 is a block and schematic diagram of circuitr for a supervisory station connection controller ' include on a monitor card used in the preferred embodiment; FIG. 8 is a block and schematic diagram of sequencin 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 circui arrangement that is replicated on an audio message car used in the preferred embodiment for generating and trans mitting 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 connec¬ tion 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 implement¬ ing an audio interface incorporating audio selection swit¬ ches; 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 cir¬ cuitry; 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 pull¬ down 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 o FIG. 29 being for communications between the supervisor computer and a controlling computer incorporated in th presently preferred embodiment; FIG. 30 is a general flow chart of overall operations involved in a second of the three processes carried out b the supervisory computer, the process of FIG. 30 being fo 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 ou 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 σomprises 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 σhart 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 inσoming 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 σertain operations generally referred to in FIG. 49, in partiσular operations to serviσe a DTMF help request; FIG. 51 is a more detailed flow chart of σertain operations generally referred to in FIG. 49, in partiσular operations to serviσe a DTMF σancel 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 σertain operations generally referred to in FIG. 49, in particular operations to service a DTMF activation or 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 ref rred to in FIG. 59, in partiσular operations involved when a transfer has been attempted; FIG. 61 σomprises FIGS. 61A and 61B, and is a more detailed flow σhart of σertain operations generally referre to in FIG. 59, in particular operations involved othe than when a transfer has been attempted; and FIG. 62 is a more detailed flow chart of certai operations generally referred to in FIG. 46, in particula operations for dumping an internal line database to th supervisory computer. Detailed Desσription FIG. 1 shows, in general bloσk diagram form, major functionalelements ofaninteractively-supervised, computer- controlled system IA organized in accord with the presently preferred embodiment of this invention. System IA provides for allocating tasks in a network for servicing incoming σalls arriving on a plurality of incoming telephone lines IB such as incoming line 1B-1. System IA comprises a line conneσtion sub-system IC arranged between inσoming telephone lines IB and a plurality of outgoing telephone lines ID suσh as line 1D-1. System IA further σomprises- a σomputer proσessing sub-system IE whiσh digitally σommuniσates with line σonneσtion sub¬ system IC. In digitally σommuniσating with line connection sub-system IC, computer processing sub-system IE provides • digitally coded commands and receives status data. Through such digital communiσation, line σonneσtion sub-system I σooperates with σomputer proσessing sub-system IE an operates under its control to provide a call extendin controller 2A (FIG. 2) capable of operating on an autonomou basis to extend incoming calls for answer and service by group of people working as service attendants in acσor with an alloσation of tasks determined by the digitall σoded σommands. System IA further includes a display means such a a video display terminal IF and manual input means such a a mouse IG for use by a person designated as a superviso in interactively controlling computer processing sub-syste IE. A keyboard IH is part of video display terminal IF and may also be used by a supervisor wlio prefers to ente supervisory commands by keyboard entry rather than throug mouse IG. A supervisory station II is σonneσted via a monito phone line U to line σonneσtion sub-system IC to provid an audio link that the supervisor uses to σonfer with a inσo ing σaller, with one or more serviσe attendants, or wit an inσoming σaller and a serviσe attendant simultaneously. In system IA, supervisory station II is a σonventional touσh-tone dial telephone instrument with a miσrophone an speaker for optional hands-free talking and listening; on of numerous alternatives involves using a headset as super visory station II. In σombination, supervisory statio II, video display terminal IF, and mouse IG provide supervisory σonsole generally indiσated as IK. Computer proσessing sub-system IE is σontinuall responsive to status data provided by line σonneσtion sub system IC to generate on video display terminal IF a human readable, σontinually updated status report by whiσh th supervisor may be prompted to use mouse IG to enter super visory σommands. Computer proσεεsing sub-system IE i responsive to suσh manually entered supervisory σommand to provide digitally σoded σommands to σause a re-alloσatio of tasks, as explained more fully below with referenσe t more detailed drawings σonσerning the σonstruσtion and opera tion of system IA. One of the advantages of the present invention is that the above-desσribed major funσtional elements and th manner in which they σooperate are suσh that system IA σa be set up in any of a variety of σonfigurations to sui the needs of any partiσular organization and faσilitat the handling of multiple inσoming σalls in an effiσien way. With respeσt to σomputer proσessing sub-system IE, th funσtions it performs divide in a general way into funσtions relating to σommuniσating with and σontrolling line σonnec- tion sub-system IC whereby inσoming σalls σan be autonomousl extended, and into functions relating to communiσating wit and σontrolling video display terminal IF whereby human readable status reports σan be displayed and the superviso σan interaσtively exerσise human σontrol over system func tions. A suitable, and presently preferred, configuratio of σomputer proσessing sub-system IE entails two physiσally separate miσroproσessor-σontrolled σomputers of the kind σommonly desσribed as personal σomputers, and a data σom- muniσation link between the two personal computers. Herein, one of these personal computers is referred to as a controll¬ ing σomputer, and the other as a supervisory σomputer. With suσh presently preferred σonfiguration, the σontrolling σomputer operates under software σontrol to σooperate with line σonneσtion sub-system IC to define σall extending σontroller 2A (FIG. 2) whiσh extends inσoming σalls to serviσe attendants on an autonomously operating basis. It should be understood that the physiσal division of σomputer proσessing sub-system IE into two separate personal σomputers is a subordinate detail. It would be suitable, for example, to employ a so-σalled "dumb terminal" with whiσh a supervisor interaσts with the system, and to σonσentrate σomputer proσessing funσtions within a single σomputer. With referenσe to FIG. 2, there will now be described a representative overall system configuration, set up for an organization having facilities in Dallas, Texas and an office in Chicago, Illinois. 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 conneσted to the publiσ switσhed network. Beσause the inσoming lines are σonneσted to the publiσ switσhed network, through a σentral offiσe 2B near the Dallas faσilities, a σaller σan originate an inσoming σall to the system from any arbitrary loσation, e.g., New York City as indiσated in FIG. 2, with the inσoming σall being routed through a nearby σentral offiσe 2C over the publiσ switσhed network to σentral offiσe 2B. The organiza¬ tion σan subsσribe to a group of inσoming toll-free lines, all appearing to have the same "800" telephone number. The routing of any inσoming σall, originated by dialin the "800" number, is effected in acσord with the standard teσhni ues of the publiσ switσhed network. . Beσause the outgoing lines are σonneσted to the publiσ switσhed network, inσoming σalls σan 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 IA 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 acσount in forming a shift of at-home serviσe attendants. Thus, when a high volume of inσoming σalls are likely to be plaσed from loσations 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 serviσe attendants to be seleσted from residents along the East Coast. As to the person who is to serve as the supervisor of the system, that person likewise σan work at any arbitrary location, e.g., in the organization's offices in Chicago. In acσord with preferred features of this invention, modems (not shown in FIG. 2) are provided to σommuniσate data over the publiσ switσhed network between call extending controller 2A located in Dallas and supervisory console IK located in Chicago. Further with respect to overall operation of system IA, 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 respeσt to usage σharges for the inσoming lines that are toll free only to the originating parties, and with respeσt to usage σharges for the outgoing lines. To provide for suσh effiσienσy, it is advantageous for the system to inσlude automatiσ dialing features to plaσe σalls to a group of multi-purpose stations suσh as at-home telephones, and aσσept these σalled stations as network stations, all just before the beginning of any period of prediσtable high volume inσoming traffiσ. System IA has suσh preferred auto atiσ dialing features as dis- σlosed in more detail below, and has further novel and advantageous features relating to aσσepting 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 IA provides automatic message transmitting features, whereby service attendants upon answering the call automatically plaσed by the system are greeted with a pre-reσorded message, alerting them that the σall being answered is one from the system, and thereby prompting the entry of a σode defining a seσurity σlearanσe signal whiσh is transmitted in DTMF (Dual Tone Multi Frequenσy) signal form to system IA. System IA provides for transmitting numerous other messages under various σircumstanσes, suσh as at the end of a shift; for transmitting musiσ, for example, while a serviσe attendant is waiting to have an inσoming σall extended; and for transmitting a prompt tone to the serviσe attendant just before an inσoming σall is to be extended. With referenσe to FIG. 3, system IA will now be desσribed at a more detailed bloσk diagram level. To emphasize basiσ features of system IA and to avoid obsσuring such basic features with subordinate detail, various matters conσerning the σoristruσtion of this speσifiσ embodimen are referenσed in FIG. 3 in general terms. One suσh matte σonσerns a matrix of line σards referenσed in FIG. 3 i general terms as line σard 3A(0,1) through line σard 3A(M,N) , where M stands for row and N stands for σolumn. In a speσifiσ embodiment, partiσularly suitable for handling a high volume of inσoming traffiσ, there are 105 line σards arranged in seven rows (0..6) and fifteen σolumns (1..15). The line σards form part of line σonneσtion sub¬ system IC that is appropriately σharaσterized as a hardware sub-system. In addition to the line σards, sub-system IC inσludes a separate row bus σorresponding to eaσh row of line σards, inσluding row (0) bus, row (1) bus, and row (M) bus. Sub-system IC further inσludes a separate bus σontroller σorresponding to eaσh row bus, inσluding bus σontroller (0) , bus σontroller (1) , and bus σontroller (M) . Sub-system IC further includes a system bus, and a plurality of system cards. As presently arranged, the specifiσ embodiment has the σapaσity to reσeive up to seven different system σards, inσluding suσh system σards 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 specifiσ embodiment is a SYS. CARD 0, which is also referred to as σom uniσations σard 3B. FIG. 3 also shows a σontrolling σomputer 3C which communiσates with line σonneσtion sub-system IC through σommuniσations σard 3B. Communiσations σard 3B has an asyn- σhronous σommuniσations interfaσe for σommuniσating with σontrolling σomputer 3C. FIG. 3 also shows supervisory σonsole IK as σomprising a remote supervisory σomputer 3D and supervisory station II. A modem phone line 3E σon- neσts remote supervisory σomputer 3D to σontrolling σomputer 3C. Controlling σomputer 3C has an internal modem whiσh is σonneσted via modem phone line 3E to a remote modem within remote supervisory σomputer 3D. Another one of the system cards, viz, SYS. CARD 1 (also referred to as monitor card 3F) σommuniσates with supervisory station II via monitor phone line 1J. Another one of the system σards, viz, SYS. CARD 2 (also referred to as audio message σard 3G) provides σirσuitry used in automatiσ message transmitting features of system IA. Eaσh line σard has an inσoming line interfaσe, an outgoing line interfaσe, and a row bus interfaσe. Line σard 3A(0,1) has its inσoming line interfaσe σonneσted to inσoming line 1B-1, and has its outgoing line interfaσe σonneσted to outgoing line 1D-1. In general, any line card can be referred to as line card 3A(i,j) , and in acσord with suσh general terminology, suσh line σard 3A(i,j) has its inσoming line interfaσe σonneσted to inσoming line 1B- [(i*15)+j] and its outgoing line interfaσe σonneσted to outgoing line lD-[(i*15)+j] . Eaσh of the line σards along a row has its row bus interfaσe σonneσted to the partiσular row bus of row bus (0) through row bus (M) that σorresponds to that row. All the bus σontrollers and all the system σards σonneσt directly to the system bus. FIG. 4 shows the line cards in place within a cabi¬ net 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 aσross the width of σabinet 4A. In accord with conventional techniques, each line σard has an edge σonnector for conneσtion to a mating, vertiσally oriented σonneσtor on suσh a motherboard. As indicated in FIG. 4, the fifteen line cards of each row are horizontally spaσed apart within σabinet 4A. Eaσh motherboard has, in addition to the fifteen σonneσtors for a row of line cards, another conneσtor for a system σard. As indiσated above, eaσh system σard σommuni¬ σates with the system bus. Eaσh motherboard also supports σirσuitry (FIG. 5) for implementing the funσtions of th bus σontroller for the σorresponding row. To provide a further general overview of the entir system before proσeeding into a detailed disσlosure o speσifiσ implementing hardware, there will now be desσribed, 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 faσilitate prompting of the supervisor. The top line of the displayed status report is referred to herein as a main menu seleσtion line. Any item on the main menu selection line σan be seleσted by the supervisor by moving mouse IG so as to position a mouse σursor to the desired item and σliσking a button on the mouse. Some of the main menu items have assoσiated sub-menus (not shown in FIG. 23) , eaσh of whiσh presents sub-seleσtions 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 informa¬ tion." This global information includes the current date and time and information conσerning a "shift"; i.e. , informa¬ tion identifying, as a group, the people who are serving as serviσe attendants, and statistiσal information ("Total σalls" 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-σoded box to aid the super- visor in interpreting σolor σoding of the displayed status report. Beneath the legend line there is a matrix display area that in this speσifiσ embodiment has 105 elements that are in one-to-one σorrespondenσe with the 105 line σards mentioned above. Each of the elements in the matrix display area comprises a box and an optional line card number. Eaσh box provides status information σonσerning a σorresponding line σard; preferably this is provided by σolor σoding the boxes. In FIG. 23, eaσh box is shaded for the σolor blue, this being the σolor used to indiσate a line σard σondition in whiσh there is no attendant on line, and software has made the line σard idle by "busying" its inσoming line. Other σolors, 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 partiσular mode, referred to hereafter as σall 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 σard. In FIG. 23, the display pointer happens to be .framing the box numbered "77." This means that the supervisor σan issue supervisory σommands targeted to affeσt the line σard that has a line σard ID of "77." If the supervisor wants to issue super¬ visory σommands targeted to affeσt a different line σard, the supervisor σan move mouse IG to position the mouse cursor at the desired box, then σliσk the mouse button, and the display pointer will jump to the seleσted box. If the supervisor desires to erase the line σard I numbers that appear in this displayed report, the superviso σan position the mouse σursor to the "Numbers" item on th main menu seleσtion line, then σliσk the mouse σurso button, and the line σard ID numbers will be erased. The "Numbers" item on the main menu selection line constitutes a toggle-type selection; i.e., sucσessive seleσtions of this item toggles the numbers on and off. If the supervisor desires to be prompted by symbols instead of σolor σoding (as when a monoσhrome display is being used) , the supervisor σan position the mouse cursor to the "Symbols" item on the main menu selection line, then cliσk the mouse button, and status-representing symbols will replaσe the σolor-σoded 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. Suσcessive 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 embodi¬ ment, 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 σirσuitry involved in σommuniσating digitally σoded σommands and status data, and audio, between σontroll¬ ing σomputer 3C and sub-system IC. FIG. 5 shows circuitry for implementing a bus controller; as stated above, eaσh motherboard has suσh a bus σontroller. FIG. 6 shows cir- σuitry for implementing σommuniσations σard 3B. Eaσh bus σontroller has essentially the same σonstruc- tion, and, for generality of reference, cirσuitry shown in FIG. 5 is identified therein as "BUS CONTROLLER (I)." This circuitry is conneσted between the system bus and row bus (I.) . The system bus has 42 parallel σonduσtors. Six of these parallel σonduσtors are referred to as an Audio Bus whiσh 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 desσribed above as part of the general overview of the system and various features it provides inσluding automatic message transmission features, etc. Each row bus has six σorresponding parallel σonduσtors, and eaσh bus σontroller direσtly σonneσts together the Audio Bus portion of the system bus and the Audio Bus portion of the row bus. This is indiσated 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 σonduσtors in the Audio Bus is indiσated in FIG. 5 by a slash and the number 6 next to the slash. This symbology of a slash and an adjaσεnt number is used throughout the drawings to indiσate the number of parallel σonduσtors that are represented as a single line. Eight other parallel σonduσtors of the system bus provide for propagating a Command Word. In FIG. 5, a funσtional bloσk 5A is used to indiσate that eight parallel Sσhmitt trigger drivers are inσluded in eaσh bus σontroller for σommuniσating each such Command Word to the σorresponding row bus. Eight other parallel σonduσtors of the system bus provide for propagating a Status Word. As indiσated in FIG. 5, a tri-state bus driver 5B is inσluded in each bus controller for seleσtively σommuniσating a Status Word from the corresponding row bus to the system bus. Eight other parallel conduσtors of the system bus are referred to as a Row Seleσt Bus whiσh provides fo propagating a one-out-of-eight seleσtion signal. As indi σated in FIG. 5, eaσh bus σontroller has a row addres seleσtor 5C σomprising a group of terminal pairs wit whiσh a jumper 5D is used to σonfigure a row address. I should be understood that one of these eight σonduσtors i a spare providing for system expansion from the seven-ro matrix of σards used in the speσifiσ embodiment being desσribed. . Four other parallel σonduσtors of the system bus provide for propagating a Card Seleσt Nibble. As indiσated in FIG. 5, a deσoder 5E is inσluded in eaσh bus σontroller for deσoding the Card Seleσt Nibble. Deσoder 5E has an enable input σonneσted to the output of an AND gate 5F. If the output of AND gate 5F is true, and a Card Seleσt Nibble is applied to deσoder 5E, then one of sixteen Card Seleσt signals will be true. A Card Seleσt 0 signal seleσts a system σard within a row. Eaσh of the remaining fifteen suσh σard seleσt signals seleσts a line σard within a row. One other σonduσtor of the system bus provides for propagating a Row Bus Disable Flag produσed by a retrig- gerable one-shot 5G in response to manual aσtuation of a row serviσe switσh 5H. One other σonduσtor of the system bus provides for propagating a 3.579 MHz Cloσk signal. Eaσh bus σontroller has a Sσhmitt trigger driver 51 for propagating this σloσk signal to the σorresponding σonduσtor of the row bus. One other σonduσtor of the system bus provides for propagating a Prompt Tone signal. The Prompt Tone signal is used for the purpose, generally desσribed within the general overview of the system, of prompting a serviσe attendant to be prepared to serviσe an inσoming σall; the Prompt Tone signal is automatiσally transmitted over an outgoing line just before an inσoming σall is extended for answer and serviσe by the serviσe attendant. Suitably, the Prompt Tone signal has a frequenσy of 400 Hz. Eaσh bus σontroller has a Sσhmitt trigger driver 5J for propagat¬ ing this Prompt Tone signal to the σorresponding conductor of the row bus. One other conduσtor of the system bus provides for propagating a Message 2 Start/Stop Strobe signal. Each bus controller has a Schmitt trigger driver 5K for propagat- ing this strobe signal to a σorresponding σonduσtor of the row bus. Four other σonduσtors of the system bus define a spare bus providing for system expansion. As shown in FIG. 6, σommunications card 3B includes a UART (Universal Asynchronous Receiver Transmitter) 6A having an ιr 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 σrystal 6C tuned to 1.8432 MHz σcoperate to provide an input σontrol signal to UART 6A to set its baud rate. With respect to the serial input data UART 6A reσeives, UART 6A performs a serial-to-parallel σonversion funσtion suσh that eaσh group of eight suσσessive bits of a byte are σonverted to parallel format and applied to an eight-σonduσtor signal path 6A-0. With respeσt to the serial output data UART 6A transmits, UART 6A performs a parallel-to-serial σonversion function suσh that eaσh eight-bit Status Word it reσeives in parallel from the system bus via a signal path 6A-I is σonverted to serial form for transmission to σontrolling σomputer 3C. Communiσations σard 3B further inσludes an 8-bit address latσh 6D, an 8-bit σo mand word latch 6E, and a 3 x 8 decoder 6F that are arranged to respond to the parallel output of UART 6A; and further includes a divider 6G tha performs a frequency dividing function in response to a output of generator 6B to produce the Prompt Tone at approx imately 400 Hz; and further includes a crystal-σontrolle σloσk sourσe 6H for producing the 3.579 MHz Clock. Th output of deσoder 6F is σonnected to the row select bu conduσtors of the system bus. The four least signifiσan bit positions of latσh 6D provide the Card Seleσt Nibbl to the system bus. ""- The 8-bit output of latσh 6E provide the Command Word to the system bus. The Prompt Tone and the 3.579 Mhz Clock are applied to the system bus. The digitally σoded σommands that σontrolling σomputer 3C issues to sub-system IC are reσeived in serial form by UART 6A. These digitally σoded σommands inσlude σommands having a two-byte format, one byte defining a σard address and another byte defining a Command Word. A σard address byte, σonverted from serial to parallel by UART 6A, undergoes two levels of deσoding, 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 sig¬ nificant nibble of the addressing byte is, after it is latσhed within part of address latσh 6D, decoded by decoder 6F so that only a selected conduσtor of the eight-σonduσtor row seleσt bus propagates a true signal whereas the remain¬ ing σonduσtors propagate a false signal. Beσause there are seven rows in this embodiment, three addressing bits suffiσe to identify a row. The most signifiσant bit of a group of eight bits transmitted from σontrolling σomputer 3C may be σoded to distinguish an address from a Command Word. If, for example, row 0 of the matrix of line σards is being addressed. Row Seleσt 0 (FIG. 5) will be true. In bus σontroller (0) , jumper 5D σonneσts a terminal pair of row address seleσtor 5C suσh that the true σondition of Row Seleσt 0 σauses the output of AND gate 5F to beσo e true (if the row has not been disabled for serviσe via aσtuation of row serviσe switσh 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 deσoder 5E to forσe the Card Seleσt 1 signal to be true, and to forσe the Card Seleσt 0 signal and eaσh of Card Seleσt 2 through Card Seleσt 15 signals to be false. The digitally coded status data that controlling computer 3C receives from line conneσtion sub-system IC are transmitted in serial form by UART 6A. The signal flow in this direσtion proσeeds from a row bus to a tri- state bus driver 5B within the σorresponding bus σontroller. The output of AND gate 5F is applied to an enable input of tri-state bus driver 5B to perform the same kind of seleσtion funσtion as has been desσribed above, whereby only one row bus at a time is seleσted to provide a Status Word to the system bus. UART 6A on σommuniσations σard 3B serializes the Status Word it reσeives from the system bus, and trans¬ mits it as its serial data output to σontrolling σomputer 3C. With referenσe to FIGS. 7 , 8, and 9, there will now be desσx'ibed σirσuitry inσluded on another system σard, viz, monitor σard 3F. Monitor σard 3F defines, among other things, th interfaσe between line σonneσtion sub-system IC and super¬ visory station II; i.e., monitor phone line 1J has one of its ends σonneσted to monitor σard 3F as shown in FIG. 7, and has its opposite end σonneσted to supervisory station II. Some of the σirσuitry shown in FIG. 7, in partiσular σirσuitry indiσated generally at 7, performs funσtions for a supervisory σonneσtion σontroller for σooperating with supervisory station II to form opposite ends of a σall σonneσtion path, other σirσuitry shown in FIG. 7 performs functions for providing status data to controlling σomputer 3C. Monitor card 3F includes command-deσoding σirσuitry (shown in FIG. 9) for producing various logiσ signals, some of whiσh σause logic and sequencing σirσuitry o monitor σard (shown in FIG. 8) to produσe other logi signals in a predetermined se uenσe. As to the deσoding circuitry depicted in FIG. 9, i includes ' three decoders 9A, 9B, and 9C, and a Schmit trigger driver 9D. The input to driver 9D is a Card Seleσ signal reσeived from row bus (1) . As indiσated by FIGS. 2 and 3, monitor σard 3F oσσupies the system slot of row 1 of sub-system IC. When the bus controller for row 1 is enabled and its decoder 5E (FIG. 5) forσes the Card Selec 0 signal to be true, cirσuit 9D enables deσoders 9A, 9B, and 9C to produσe a valid deσoded output in response to the Command Word being propagated to monitor σard 3F fro σontrolling σomputer 3C via the system bus, Sσhmitt trigge drivers 5A (FIG. 5) , and row bus (1) . • The circuitry depicted in FIG. 9 also includes a Sch itt trigger driver circuit 9E and a Schmitt trigger driver σirσuit 9F. Cirσuit 9E provides for buffering the 3.579 MHz σloσk. Cirσuit 9F provides for buffering a Message 2 Start/Stop Strobe. As shown in FIG. 7, σirσuitry 7 of the supervisory station σonneσtion σontroller inσludes an inσomingtransient- surge suppressor 7A conneσted aσross monitor phone line LT, Tip and Ring lines, and a diode bridge 7B σonneσted between monitor phone line 1J and the Tip and Ring lines to ensure σorreσt polarity for DC potential of the Tip line relative to the Ring line. Cirσuitry 7 further inσludes a transformer 7C having a σapaσitor 7D σonneσted in parallel with its primary winding, a zener diode 7E, a hook switσh simulating σon- trollable switσh 7F, whiσh is a relay. While switσh 7F is σlosed and DC loop σurrent flows through it, such DC loop σurrent flows from the Tip line, through the primary winding of transformer 7C, through zener diode 7E, through the σlosed switσh 7F, to the Ring line. While suσh loop σurrent flows, a voltage is developed across zener diode 7E. loop-σurrent deteσting σirσuit 7G is connected to be respon¬ sive to the voltage developed across zener diode 7E, and includes a switching transistor that is on only while loop current is flowing. Circuitry7 further inσludes a ground-start simulating σontrollable switσh 7H that, like hook switσh simulating σontrollable switσh 7F, is a relay. Cirσuitry 7 further provides for sensing and deteσting a ringing signal. In partiσular, a ringing-signal deteσting σirσuit 71 has its input AC σoupled aσross the Tip and Ring lines, and has a switσhing transistor that is on if a ringing signal is present. The σontrollable ' switσhes of σirσuitry 7 operate in aσσord with logiσ signals, the values of whiσh are determined by σommands that are issued by σontrolling σomputer 3C. One of the logiσ signals produσed by the sequenσing σirσuitry depiσted in FIG. 8 is identified in FIG. 8 as "CTL 90— Line Conneσt 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 acσord with a notational σonventionused generally throughout the drawings to indiσate how various σirσuits on separate drawing figures are inter- σonneσted. Also, as part of the notational σonvention, the terms "Control," "Strobe," and "Status Bit," are used to indiσate the nature of a signal. The term "Control" applies to a signal that has either a true value to es- tablish a σontrol σondition or a false value to establish an opposite σontrol σondition. The term "Strobe," applies to a signal having a pulse format for initiating or terminat- ing an operation. The term "Status Bit" applies to a signal σontaining information to be provided to controlling computer 3C is a part of a group defining a Status Word. Further with respeσt to logiσ signal notation, the σirσuitry shown throughout the drawings uses "positive logiσ σontrol." For example, a true logiσ level for the CTL 90 σontrol signal σauses the switσh it σontrols, viz, switσh 7F, to close; otherwise the switch 7F is open. In addition to the Line Conneσt Control signal (CT 90) desσribed above, a Ground Line Control signal (CTL 86) is produσed by the sequencing cirσuitry depicted in FIG. and used to control cirσuitry 7. More partiσularly, thi CTL 86 signal is used to σontrol ground start simulatin switσh 7H. A CK signal (CTL 80) is a buffered σloσk signa provided by driver 9E (FIG. 9) , and is applied as a trigge input to each of two retriggerable one-shots 7J and 7K. One-shot 7J responds to loop-current detecting cirσuit 7 to produσe a Line Current status Bit signal (STA 8) . One shot 7K responds to ringing-signal deteσting σircuit 71 t produce a Ring Detect Status signal (STA 9) . The seσondary winding of transformer 7C is σonneσte to a σontrollable switσh 7L that defines a σontrollabl inter-σonneσtion means arranged between the σonnectio controller circuitry 7 and a conduσtor of the Audio Bu used for propagating a Monitor Audio Signal (AUD 4) . Controllable switσh 7L is a field effeσt transistor (FET) a suitable alternative is a relay. Controllable switσh 7 is σlosed while an Audio Conneσt Control signal (CTL 91) is true; otherwise it is open. The logic level of th Audio Connect Control signal is determined by cirσuitr depiσted in FIG. 8 in aσσord with signals produσed by th σommand-deσoding σirσuitry shown in FIG. 9. A σirσuit node is defined where σontrollable switσ 7L and the seσondary winding of transformer 7C are interσon neσted. Four other σontrollable switσhes 7M, 7N, 70, an 7P are also σonneσted to that circuit node. In operatio of system IA, no more than one of these four switches i closed at any one time. During the time that a call i being plaσed to a remote supervisor, switσh 7M is σlosed and the output of a DTMF generator 7Q is σoupled throug switσh 7M so as to dial a telephone number at whiσh th remote supervisor σan be reaσhed. Before suσh dialin commences, a sequence of operations is performed, under σontrol of σontrolling σomputer 3C; the sequenσe inσludes loading DTMF generator 7Q with a selected telephone number, closing switch 7F to simulate an off hook condition, operat- ing switch 7H in acσord with σonventional ground start line protoσol so that dial tone will be requested, and then σausing DTMF generator 7Q to output the stored telephone number for the supervisor. Switσhes 7N, 70, and 7P provide switσhing σontrol for propagating, respeσtively, Message 1 Audio (AUD 6) , Message 2 Audio (AUD 7) , and Message 3 Audio (AUD 8) . These three audio signals are used in the auto atiσ message transmitting feature. A DTMF reσeiver 7R has its input σapaσitively con- neσted to the above-mentioned node to whiσh the foregoing numerous switσhes are σonneσted; receiver 7R provides for detection of in-band signals used in the operation of system IA. A decoder 7S responds to the parallel output signal of reσeiver 7R to produσe eight different strobe signals that are identified in FIG. 7. The σirσuitry depiσted in FIG. 7 further inσludes σirσuitry for defining the information σontent of a Status Word to be provided to σontrolling σomputer 3C regarding conditions of operation of monitor card 3F. This σirσuitry inσludes a three-stage bus driver and multiplexer 7T, and a three-stage, four-bit latσh 7U. Multiplexer 7T has an "A Enable" σontrol input and a "B Enable" σontrol input that reσeive, respeσtively, a Status A Control signal (CTL 78) and a Status B Control signal (CTL 77) . These control signals are produced by decoder 9C (FIG. 9) in response to digitally coded commands issued by σontrolling computer 3 ' C. When controlling σomputer 3C issues a digitally σoded σommand to obtain Status A data from monitor σard 3F, deσoder 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 inσlude Ground Return, i.e., a false logiσ value; the Audio Conneσt Control signal (CTL 91) ; an On-Hook Timer Status Bit signal (STA 10) ; and the Line Current Status Bit signal (STA 8) . When σontrolling σomputer 3C issues a digitally σoded σommand to obtain Status B data from monitor σard 3F, deσoder 9C forσes 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 σommand to obtain Status A data from monitor σard 3F, deσoder 9C forσes the Status A Control signal (CTL 78) to be true. In response, latσh 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 reσeiver 7R, i.e., the CTL 82, CTL 83, CTL 84, and CTL 85 signals. Latσh 7U σopies these signals when¬ ever 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 funσtions, a representative example of whiσh has been generally desσribed above σonσerning the sequenσe of operations involved in going off-hook and dialing the supervisor. The σirσuitry of FIG. 8 inσludes a busy line flip flop 8A that, like other flip flops and other bit-storing deviσes desσribed below, has a Q output and a Q output. In the σase of flip flop 8A, only the Q output is σonneσted to other σirσuitry. While flip flop 8A is in its set state, its Q output produσes a true logiσ level signal, and its Q output produσes a false logiσ 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 produσed by deσoder 9A (FIG. 9) in response to digitally σoded σommands issuedby σontrolling σomputer 3C. The Q output of flip flop 8A is σonneσted to one input of a two-input OR gate 8B, the output of whiσh produσes the Ground Line Control signal (CTL 86) for σon¬ trolling ground start simulating switσh 7H (FIG. 7) . The σirσuitry of FIG. 8 further inσludes a gate 8C that produσes 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 produσed by deσoder 9A (FIG. 9) in response to digitally σoded σommands issued by σontrolling σomputer 3C. The On-Hook Timer Status Bit signal is produσed by an on-hook timer σirσuit 8E. Phone line flip flop 8D is reset when the output of an OR gate 8F is true; this oσσurs if either an On-Hook Control signal (CTL 58) or an Aσtivate Timer End Strobe signal (STB 23) beσomes true. The On-Hook Control signal is produσed by the decoder 9A - (FIG. 9) in response to digitally coded σommands issued by σontrolling σomputer 3C. The Aσtivate Timer End Strobe signal is produσed by a timer-end one- shot σirσuit 8G. The σirσuitry of Fig. 8 further inσludes a disσonneσt timer σirσuit 8H that has a trigger input and a clear input. When triggered, disconneσt timer 8H initiates a sequenσe of operations involved in playing amessage (messag 2) to the supervisor and then terminating the σall σonneσtio path between supervisory station II and monitor σard 3F. Message 2 in this embodiment has a duration of approximatel ten seσonds, and is σyσliσally generated. To ensure tha the full message is played from start to finish, disconneσ timer σirσuit 8H provides a timing interval having a maximu duration of twiσe the length of the message, i.e., twent seσonds. The trigger input of disσonneσt timer σirσuit 8H i σonneσted to the Q output of flip flop 8D. A false-to true transition in the signal produced by the Q output o flip flop 8D, triggers disσonneσt timer σirσuit 8H to star to define its timing interval. During this timing interval the Q output of disσonneσt timer 8H is true. This forσes the output signal of an OR gate 81 to remain true; it ha been true beσause the signal produσed by the Q output o flip flop 8D had been true until disσonneσt timer 8H was triggered. The output signal of OR gate 81 is the Lin Conneσt Control signal (CTL 90) that σontrols hook-switc simulating switch 7F (Fig. 7) . Thus, hook switch 7F con¬ tinues to simulate an off-hook condition while the timin interval defined by disconneσt timer 8H is in progress. Also while the signal produced by timer σirσuit 8H is true, a message 2 flip flop 8 is enabled to respond to the Message 2 Start/Stop Strobe signal (STB 13) whiσh is applied to its toggle input. When the STB 13 strobe oσσur while the signal produσed by disσonneσt timer 8H is true, message 2 flip flop 8J σhanges state. The output signa it produσes, a Message 2 Control signal (CTL 89) , σontrol switσh 70 (FIG. 7) ♦ so that a Message 2 Audio signal (AU 7) is gated through by the supervisory station σonneσtio σontroller σirσuitry 7. Thus, this CTL 89 signal beσome true only at the start of a given σyσle of message 2, an only if disconnect timer 8H has initiated the sequence o operations for terminating the call connection path betwee supervisory station II and monitor card 3F. The true-to false transition in the signal produσed by OR gate 8 triggers on-hook timer 8E. The timing interval-provide by on-hook timer 8E is suitably two seσonds; this duratio is suffiσiently long as to prevent any ambiguity with a "hook flash" type operation of amomentary on-hook σondition. The σirσuitry of Fig. 8 further inσludes a group of sequenσing σirσuits 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 conneσted to one of the inputs of OR gate 8B. Thus, while the signal produσed by one-shot 8K is true, it forσes the Ground Line Control signal (CTL 86) to be true. This in turn σauses ground-start simulating switσh 7H (Fig. 7) to close temporarily, so as to stimulate the sourσe of dial tone to provide it before automatiσ dialing σommenσes. Suitably, dial tone one-shot defines a 0.5 seσond pulse for this purpose. Delay one-shot 8L is triggered by the true-to-false transition in the pulse signal produσed by dial tone one- shot 8K and defines a delay period suffiσiently long to allow for the sourσe of dial tone to reaσt and to provide the dial tone. Suitably, this delay period is one seσond. The true-to-false transition in the signal produσed by delay one-shot 8L triggers dial one-shot 8M to forσe a DTMF Dial Control signal (CTL 87) to beσo e true. This CTL 87 signal is σoupled through diodes to R4 and C_ inputs of DTMF generator 7Q. These inputs in σombination σorrespond to the "#" symbol; the parallel signals σoupled through the diodes initiate the dialing. This CTL 87 signal also controls switσh 7M (FIG. 7) so that the automatiσ telephone number dialing output signal of DTMF generator 7Q is gated throughby the supervisory station σonneσtion σontroller cir¬ cuitry 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 telephon number to be dialled to reach supervisory station II. The true-to-false transition in the CTL 87 signal triggers aσtivate timer σircuit 8N to start defining a verification timing interval, preferably having a maximum duration of 30 seconds. The Q output of aσtivate timer 8N produσes a Message 1 Control signal (CTL 88) . This CTL 88 signal σontrols switσh 7N (FIG. 7) to provide for seleσtively 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 cirσuit 8N has a σlear 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 seσurity-σlearance signal is provided. This strobe signal is also applied to a disable input of an activate abort one-shot 80 which has its trigger input conneσted to the Q output of aσtivate timer σirσuit 8N and whiσh produσes a System Initialize Strobe signal (STB 30) . If the seσurity verifiσation signal is provided within the maximum time allotted by timer σirσuit 8N, then the STB 20 signal σlears timer σirσuit 8N and at the same time disables one-shot 80 from being triggered. If timer σirσuit 8N σompletes 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 80, thereby σausing a true pulse to be defined in the STB 30 signal. The oσσurrenσe of a true pulse in the STB 30 signal, in effeσt, aborts this sequenσe of events involved in plaσing a σall to a super¬ visor. It does so by resetting all timers, one-shots, and flip flops on monitor σard 3F. This same resetting function is subject to software control. That is, controlling σomputer 3C issues a σommand for monitor σard 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 σontrol, σontrolling σomputer 3C, as will be explained below, provides for σounting the number of tries to plaσe suσh a σall 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 conneσt flip flop 8Q, an OR gate 8R, and a message 3 flip flop 8S. AND gate 8P produσes a signal to σontrol the σlear input of disconnect timer 8H, in response to two signals, viz, the STB 13 signal and the CTL 89 signal. Audio conneσt flip flop 8Q has a set input that responds to an Audio On Control signal (CTL 68) produσed by deσoder 9B (FIG. 9) in response to digitally σoded σommands issued by σontrolling σomputer 3C. The output of flip flop 8Q produces the Audio Connect Control signal (CTL 91) that controls inter-conneσtion switσh 7L (FIG. 7) . As to OR gate 8R, the signal it produσes 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 produσed by deσoder 9B (FIG. 9) in response to digitally σoded σommands issued by σontrolling σomputer 3C. Another of these four signals is the Message 1 Control signal (CTL 88) produσed by aσtivate timer 8N. Another of these four signals is the Message 2 Control signal (CTL 89) produced by message 2 flip flop 8 . 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 σoded σommands issued by σontrolling σomputer 3C. Message 3 flip flop 8S produσes the CTL 92 signal that σontrols switσh 7P (FIG. 7) to provide for seleσtively gating Message 3 Audio (AUD 8) for transmission by the system. With referenσe to FIGS. 10-13, there will now be desσribed σirσuitry inσluded on audio message σard 3G whiσh oσσupies the system slot within row 2 of line σonneσ¬ tion sub-system IC. The funσtions audio message σard 3G performs relate to generation of the four messages that system IA automatiσally transmits at selected times. (Three of these messages apply equally to a supervisor or to any attendant; one of them applies speσifiσally to an attendant at the end of a shift.) To perform these funα- tions, audio message σard 3G σooperates with σontrolling σomputer 3C via row bus (2) , the system bus, and σommuniσa¬ tions σard 3B to reσeive digitally σoded σommands and to provide status data. The σirσuitry on audio message σard 3G for deσoding digitally σoded σommands is shown in FIG. 12. The σirσuitry on audio message σard 3G for applying status data to the status bus is shown in FIG. 13. Three of the messages that system IA automatiσally generates and transmits are generated by three identiσal σirσuit arrangements. FIG. 10 shows such a circuit arrange¬ ment, and sets out references in general terms such as "Channel i." It should be understood that this cirσuit arrangement is repliσated three times suσh 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 σirσuit arrangement, shown in FIG. 11, that, in most respeσts exσept those speσifiσally desσribed, is identiσal to the σirσuit arrangement of FIG. 10. The σirσuitry shown in FIG. 10 inσludes an audio σonneσt flip flop 10A, a switσh 10B σontrolled by flip flop 10A, and a speeσh proσessor IOC. In the preferred embodiment, speeσh proσessor 10C is an OKI 6258 Solid State Reσorder Speeσh Proσessor integrated σirσuit σhip. It handles analog-to-digital and digital-to-analog σonver¬ sion, and operates in cooperation, with a σrystal 10D, tuned to 4 MHz in this embodiment. It has numerous outputs, including a "DA OUT" output and a "V Clock" output which are σonneσted to a low pass filter 10E. A buffer amplifier is σonneσted between the output of low pass filter 10E and switσh 10B. Another output of .speeσh proσessor IOC 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 σard 3G so as to provide an indiσation to maintenanσe personnel for use in serviσing the system. Another output of speeσh proσessor IOC 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 speeσh proσessor IOC are σonneσted to a 19-σonduσtor address bus used to propagate addressing signals to a message memory array generally indiσated at 10G. Eight ROM σhips are arranged in parallel to define this message memory array. One at a time of these eight ROM σhips is seleσted by a one-out-of-eight seleσt signal produσed by a deσoder 10H. The seleσted ROM chip responds to the addressing signal provided by speech processor IOC to apply an eight bit byte to a data bus σonneσting the output to the ROM σhips to a data input of speeσh proσessor IOC. Deσoder 10H deσodes a three-bit wide signal produσed by a latσh 101. The input signals applied to latσh 101 are three parallel bits supplied as part of a σommand wor issued by σontrolling σomputer 3C, and a σontrol signa for latσh σontrol whiσh is produσed by σommand-deσodin σircuitry shown in FIG. 12. Speeσh proσessor IOC reσeives three σontrol signals direσtly from the σommand-deσoding σirσuitry of FIG. 12; these are an All Clear Control signal, a Flag Reset Control signal, and a Pause Control signal " . Speeσh proσessor IO reσeives another σontrol signal from the output of an O gate 10J whiσh responds to a Start/Stop Control signal an a Restart Strobe signal. The Start/Stop Control signal is produσed by the σommand-deσoding σirσuitry shown in FIG. 12. The Restart Strobe signal is produσed by a one-shot 10K that is triggered by a signal produσed by one-shot 10L. As stated above, the σircuitry shown in FIG. 10 represents one of three cirσuit arrangements having identiσal σonstruσtion for handling a respeσtive one of three messages the system ' automatiσally generates and transmits. The following σross-referenσe table provides information about how the σommand-deσoding σirσuitry of FIG. 12 is interσon- neσted to these three σirσuit arrangements, whiσh are referred to .in the table as Channel 1, Channel 2, and Channel 3. Cross-Referenσe Table Regarding Channel 1, Channel 2, and Channel 3 Signals Signal C or STB No. Audio Conneσt Control Audio Disconnect Control All Clear Control Flag Reset Control Pause Control II II Cross-Referenσe Table Regarding Channel 1, Channel 2 . and Channel 3 Signals Signal C annel CTL or STB No. Start/Stop Control Restart strobe ROM 5 Seleσt Control II II ROM 6 Seleσt Control II II Cross-Referenσe Table Regarding Channel 1, Channel 2, and Channel 3 Signals Signal Channel CTL or STB No. ROM 7 Seleσt Control II II Message Audio It II Start/Stop Strobe II II Restart Strobe II II Play Baσk Status Bit II II Reσord status Bit Overload Status Bit II Memory Seleσt Control Bit 0 II II Memory Seleσt Control Bit 1 II II Memory Seleσt Control Bit 2 II As to the fourth kind of message that the system automatiσally generates and transmits, referenσe is made to FIG. 11. The referenσe numbers used in FIG. 11 are correlated with those used in FIG. 10 so as to indicate cirσuit elements that are identiσal. For example, audio σonneσt flip flop 11A (FIG. 11) has the same σonstruσtion and operation as audio σonneσt flip flop 10A (FIG. 10) . The cirσuitry of FIG. 11 differs from that of FIG. 10 in the following respeσts. First, message memory array 11G inσludes a RAM; i.e., it is written into as well as read from during normal operation of the system in σontrast to the all-ROM σonfiguration of message memory array 10G (FIG. 10) . Seσond, additional outputs of speeσh proσesso 11C are used in the σirσuit arrangement of FIG. 11; these are the CAS and RAS outputs that are σonneσted to σor¬ responding inputs of a four megabyte RAM σhip 11M of message memory array 11G. Third, three of the inputs in speeσh processor 11C, viz, the CA1, CA2, and CA3 inputs, are σonneσted differently. In partiσular, the CA1 input is connected to the Q 2 output of latch 111 (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 UN, and the CA3 input is connected to the output of an AND gate 110. AND gate UN has two inputs, one conneσted to the most signifiσant of these three bit positions ( 2 ) , and the other σonneσted to the next most signifiσant bit position (Q_) . AND gate 110 has two inputs, one σonneσted to the most signifiσant of these bit positions (Q 2 ) , and the other σonneσted to the least signifiσant bit position (Q 0 ) . The remaining differenσes involve additional σirσuits for switchably applying an audio signal to speech processor 11C so that such audio signal σan be digitized and stored in the message memory array 11G. The additional σirσuits are an audio σonneσt flip flop IIP, a switσh 11Q σontrolled by flip flop IIP, a buffer amplifier 11R through whiσh the audio signal propagates to switσh 11Q and, while switσh 11Q is σlosed, through a low pass filter IIS to an input of speeσh proσessor 11C. With referenσe to Fig. 12, the σommand-deσoding σirσuitry for audio monitor σard includes four decoder σirσuits 12A, 12B, 12C, and 12D, eaσh of whiσh is enabled by a pair of enabling signals to deσode Bits 0-3 of the σommand word reσeived via the σommand word bus portion of the system bus. One of the enabling signals is produσed by a Schmitt trigger driver cirσuit 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 σommand word. With referenσe to FIG. 13, the σircuitry shown therein provides for communiσating 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 13 , 13B, 13C, and 13D. Having completed the description of the construσtion of the various cirσuit arrangements of the three system σards, there will now be desσribed, with referenσe to FIGS. 14-22, the σonstruσtion of a line σard. As stated above, this speσifiσ .embodiment of the present invention has 105 line σards, every one of whiσh has the same σonstruσ¬ tion. 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 IC, for main- tenance or the like without necessitating a system shut down. Further-, the modular arrangement is advantageous wit respect to system expansion; as indicated above, a variet of provisions have been made to facilitate any such syste expansion. This modular architecture is further advantageou in that each line .card defines a module having its ow hardware sequenσing σirσuitry suσh that a sufficient numbe of sequencing functions are σontrolled at the line σar level to provide for autonomous operation of σall extendin operations. Thus, even if a power failure or other untowar event interrupts the operation of σontrolling σomputer 3 during a peak period of inσoming traffic, each line car can continue to operate to extend a sequence of incomin σalls. To provide an introduction to the construction of a line card, there will now be described the functional bloc diagram of FIG. 14. The Tip and Ring lines of an incomin phone line are connected to an incoming line connection controller 14A. To ensure a suffiσient power level fo audio signals propagated by the phone lines, eaσh suσ inσoming phone line is suitably connected to the output of a conventional voice frequenσy repeater VFR (not shown) . FIG. 14 also shows the Tip and Ring lines of a outgoing phone line and an outgoing line σonneσtion σon¬ troller 14B that is σonneσted to the outgoing phone line. An audio seleσtor inter-connection switch 14C is arrange between controllers 14A and 14B. (Circuitry for lin conneσtion σontrollers 14A and 14B and σircuitry for inter connection switch 14C are shown in FIG. 15.) Switch 14C is connected to a row bus interface whic includes an audio interface 14D, a deσoder for σommands an speσial function inputs 14E, and a tri-state bus drive 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 statu 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 An Status" whiσh σonneσt to the row bus. FIG. 14 shows, above the row bus interfaσe, lines σonneσting the row bu interfaσe to eaσh of the remaining funσtional bloσks o 1 the line card. These inσlude, in addition to bloσks 14A- 14C mentioned above, a traffiσ mode σontroller 14G, a DTMF number generator and register 14H, and in-band signal deσoder and sourσe disσriminator 141, and a broadcast mode 5 controller 14 . (Cirσuitry that performs funσtions of traffiσ mode σontroller,14G is shown in FIG. 19. Cirσuitry for DTMF generation and deσoding is shown in FIG. 20.) With referenσe to FIG. 15, there will now be described circuitry for implementing- conneσtion σontrollers 14A and 0 14B and inter-connection switch 14C. Circuitry generally indiσated at 14A in FIG. 15 performs funσtions for a station connection controller for cooperating with an originating station to form opposite ends of a σall connection path. This circuitry is implemented bythe same components arranged 5 in the same way as the cirσuitry for supervisory station σonnection controller 7 (FIG. 7). Circuitry generall indicated at 14B in FIG. 15 performs functions for a station conneσtion σontroller for σooperating with a multi-purpose station to form opposite ends of a σall σonneσtion path. 0 This σirσuitry is also implemented by the same components arranged in the same way as the circuitry for the above mentioned station conneσtion σontrollers. Inter-σonneσtio switσh 14C is implemented by a FET switσh just as switσ 7L (FIG. 7) is, within monitor card 3F. 25 As to controller 14A, it includes σontrollabl switσhes and σirσuitry for produσing signals representin σonditions of operation of σontroller 14A. The σontrollabl switσhes are 'an - inσoming line ground-start simulatin switσh 15A, and an inσoming line hook-switσh simulatin 30. switσh 15B. The circuitry of controller 14A for producin the σondition-representing signals inσludes a one-sho 15C, and two retriggerable one-shots 15D and 15E. One shot 15D produσes an Inσoming Line Current Status Bi signal (STA 2) , and is responsive to a σurrent deteσ 35 circuit that is conneσted in the same way that σirσuit 7 (FIG. 7) is σonneσted within the supervisory station σonneσ¬ tion σontroller 7. Thus, the STA 2 status bit signal it produσes is true while opposite ends of a σall σonneσtion path are σompleted; in other words, an originating party is off-hook and hook switch simulating switch 15B is simulat¬ ing an off-hook condition.. One-shot 15E produσes an Inσoming Line Ring Deteσt Status Bit signal (STA 3) . One-shot 15E is responsive to a ring deteσt σirσuit that is σonneσted in the same way that σirσuit 71 (FIG. 7) is σonneσted 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 produσes an Inσoming Line Current Termination Strobe signal (STB 0) , and is triggered by the STA 2 status bit signal produσed by one-shot 15D. As to the σontroller 14B, it inσludes σontrollable switσhes and circuitry for producing signals representing conditions of operation of controller 14B. The controll¬ able switches are an outgoing line hook-switch simulating switch 15F, and an outgoing line ground-start simulating switch 15G. The cirσuitry of σontroller 14B for produσing theσondition-representing signals inσludestworetriggerable one-shots 15H and 151. One-shot 15H produσes an Outgoing Line Ring Deteσt Status Bit signal (STA 0) , and is responsive to a ring detect circuit that is connected in the same way that cirσuit 71 (FIG. 7) is σonneσted 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 151 produces an Outgoing Line Current Status Bit signal (STA 1) , and is responsive to a current detect σirσuit that is σonneσted in the same wa that σirσuit 7G (FIG. 7) is σonneσted within the supervisor station connection controller 7. Thus, the STA 1 status bit signal it produσes 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 switσh simulating switσh 15B is simulating an off-hook σondition. As to inter-σonneσtion switσh 14C, it is σonneσted between σontroller 14A and 14B. One end of switσh 14C is also σonnected to a conduσtor used to propagate an Inσoming Line Audio signal (AUD 1) . The opposite end of switσh 14C is σonneσted to a conductor used to propagate an Outgoing Line Audio signal (AUD 0) . With reference to FIG. 16, there will now be described cirσuitry for implementing an audio interfaσe inσorporating audio seleσtion switσhes. This circuitry includes eleven controllable switches 16A - 16K, each of which is preferably implemented by a FET. Eaσh of switches 16A - 16C has one end conneσted to the σonduσtor used to propagate the Inσoming Line Audio signal (AUD 1) . As indiσated by the arrangement of σontrollable switches 16A - 16C, the Incoming Line Audio signal (AUD 1) can be any one of three signals depending upon which one, if any, of switσhes 16A - 16C is σlosed. The Inσoming Line Audio signal (AUD 1) will be the Message 4 Audio signal (AUD 9) if switσh 16A is σlosed; the Musiσ Audio signal (AUD 5) if switσh 16B is σlosed; the Monitor Audio signal (AUD 4) if switσh 16C is σlosed. Eaσh of switσhes 16D - 16K has one end σonneσted to the σonductor used to propagate the Outgoing Line Audio signal (AUD 0) . As indicated by the arrangement of σontroll¬ able switσhes .16D - 16K, the Outgoing Line Audio signal (AUD 0) σan be any one of eight signals depending upon whiσh one, if any, of switσhes 16D - 16K is σlosed. The Outgoing Line Audio signal (AUD 0) will be the Monitor Audio signal (AUD 4) if switσh 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 σlosed; 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 161 is closed; the Prompt Tone Audio (AUD 3) if switch 16 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 switσhes; these resistors provide for individually adjusting the sound level of eaσh of the various audio signals and, therefore, implement the audio interfaσe funσtion indiσated in bloσk 14D (FIG. 14) . With referenσe to FIG. 17, there will now be described cirσuitry for σontrolling the audio seleσtion switσhes. This σirσuitry inσludes a monitor flip flop 17A and a monitor side flip flop 17B, whiσh perform funσtions involved in seleσtively propagating audio signals between the par¬ tiσular line σard and supervisory station II. Flip flop 17A produσes the Monitor Status signal (STA 6) . .An audio σonneσt flip flop 17C produσes the Audio Conneαt Control signal (CTL 44) that σontrols inter-σonneσtion switσh 14C. Audio σonneσt flip flop 17C is set by a signal produced by an OR gate 17D and is reset by a signal produσed 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 171, 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 switσh 16G (FIG. 16) to σlose to propagate the -Message 3 Audio signal (AUD 8) as the Outgoing Line Audio signal (AUD 0) . To provide an option whether, when a σaller hangs up, to play message 3 audio to the attendant, an option jumper σontrols whether the STB 0 signal, whiσh is produσed by one-shot 15E (FIG. 15) , is applied to OR gate 171 so as to set message 3 flip flop 17H when inσoming line σurrent has terminated. The CTL 47 signal is also applied to one of the inputs of a NOR gate 17K. • The signal NOR gate 17K produσes is an Outgoing Line Music Control signal (CTL 40) . It is true if and only if every one of the signals applied to its inputs is false. Thus, while the CTL 47 signal is true, thereby causing the Message 3 audio signal to be propagated, the CTL 40 signal is false. While the CTL 40 signal is false, switσh 16E (FIG. 16) is open, preventing musiσ audio from being propagated as the Outgoing Line Audio signal. In effeσt, the Music Audio signal. constitutes the default Outgoing Line Audio signal. This is so because if none of the other possible audio signals have been selected, whereby every input signal to NOR gate 17K is false, then the Musiσ Audio signal propagates as the Outgoing Line Audio signal. The σontrol σirσuitry of FIG. 17 further inσludes AND gates 17L and 17M, and a NOR gate 17N; The input signals for AND gate 17L are supplied by the Q output of flip flop 17A and the Q output of flip flop 17B. The signal AND gate 17L produσes is an Outgoing Line Monitor Control signal (CTL 41) whiσh, while true, σauses switσh 16D (FIG. 16) to σlose to enable the supervisor to σonfer with a serviσe attendant whose multi-purpose station is σonneσted to the line σard outgoing line. The input signals for AND gate 17M are supplied by the Q output of flip flop 17A and the Q output of flip flop 17B. The signal AND gate 17M produσes is an Inσoming Line Monitor Control signal (CTL 42) whiσh, while true, σauses switσh 16C (FIG. 16) to σlose to enable the super- visor to σonfer with a σalling party whose originating station is conneσted to the line σard inσoming line. The CTL 42 signal is also applied as one of the input signals to NOR gate 17N. The signal NOR gate 17N produσes is a Incoming Line Music Control signal (CTL 43) . It is tru if and only if every one of the signals applied to its inputs is false. Thus, while the CTL 42 signal is true, thereby causing an inter-conneσtion whereby the superviso can confer with a calling party, the CTL 43 signal is false. While the CTL 43 signal is false, switch 16B (FIG. 16) is open, thereby preventing music audio from bein propagated as the inσoming line audio signal. In effect, the music audio signal σonstitutes the default inσomin line audio signal. This is so for the same reasons se forth above with respeσt to the outgoing line audio signal. With referenσe to FIG. 18, there will now be desσribe some of the sequenσing σirσuitry provided on eaσh lin σard. A number of the σirσuits shown in FIG. 18 have th same σonstruσtion and operation as σirσuits desσribed abov with referenσe to FIG. 8 σonσerning sequenσing σirσuitr for the monitor σard 3F. For example, a dial tone one-sho 18K (FIG. 18) has the ' same σonstruσtion and operation as one-shot 8K (FIG. 8) . Similar referenσe numbers are used in FIG. 8 and FIG. 18 for other suσh similar σirσuits (18E, 18G, 18H, 181, 18J, 18L, 18M, 18N, and 180). As to on-hook timer 18E, like on-hook timer 8E, the signal i produces is an On-Hook Timer Status Bit (STA 5 in the case of on-hook timer 18E) . In addition, this signal is also referred to as an On-Hook Strobe signal (STB 2) . The sequencing cirσuitry of FIG. 18 further inσludes an off-hook flip flop 18R and an on-hook flip flop 18S. Flip flops 18R and 18S provide for keeping traσk of th pendenσy of deσoded σommands, until sequenσes of operatio for these σommands have been exeσuted. At the end of sequenσe to disσonnect an attendant, on-hook timer 18 forces the STB 2 signal true temporarily, and this reset on-hook flip flop 18S. When timer end one-shot 18G forσes the STB 1 signal true temporarily, this resets off-hook flip flop 18R. The sequencing cirσuitry of FIG. 18 further inσludes an outgoing line σonnect flip flop 18T. Flip flop 18T is set by a signal produced by an OR gate 18U, and is reset by a signal produced by an OR gate 18V. One of the signals supplied as an input to OR gate 18V is produced by a NOR gate 18W. The arrangement of flip flop 18S, NOR gate 18W, and OR gate 18V defines the σonditions under whiσh flip flop 1ST will be reset. With respeσt to the setting of flip flop 18T, the σircuitry which defines the conditions for setting it are OR gate 18U, an OR gate 18X, a NOR gate 18Y, and flip flop 18R. When flip flop 18T changes state from its reset state to its set state, this initiates a sequence of timing operations in automatiσally placing an outgoing call to a multi-purpose station, and verifying that the person who answers the σall at the multi-purpose station is authorized to be a serviσe attendant. The details of this sequenσe are desσribed below as part of a desσription of operation in response to a digitally σoded σommand issued by σontroll¬ ing σomputer 3C. Briefly, during this sequenσe, an Outgoing Line Ground Control signal (CTL 51) , produσed by dial tone one-shot 18K, is temporarily forced true, and this causes ground start simulating switch 15G to close temporarily. Also during this sequenσe, an Outgoing Line Conneσt Control signal (CTL 55) , produσed by OR gate 181, is forσed true, and this σauses hook switσh simulating switσh 15F (FIG. 15) to σlose. With switσh 15F closed, and switch 15G temporarily closed, dial tone will appear on the outgoing line. Then, automatic dialing can proσeed. Also during this sequenσe, dial one-shot 18M temporarily forσes tru the DTMF Dial Control signal (CTL 52) . While the CTL 52 signal is true, switσh 16K (FIG. 16) is σlosed and propagate the DTMF Dial Audio signal (AUD 2) as the Outgoing Lin Audio signal (AUD 0) . With referenσe to FIG. 19, there will now be desσribe σirσuitry that performs funσtions of tra fiσ mode controlle 14G. This cirσuitry inσludes an inσoming line hardware bus flip flop 19A, the Q output of whiσh is σonneσted to an inpu of an OR gate 19B. An inσoming line software busy flip flo 19C has its Q output σonneσted to another input of OR gat 19B. If either hardware-busy flip flop 19A or software-bus flip flop 19C is in its set state, then OR gate 19B forσes an Inσoming Line Busy Control signal (CTL 48) true. Th Inσoming Line Busy Control signal (CTL 48) σontrols groun start simulating switσh 15A (FIG. 15) . An invertor 19 responds to the CTL 48 signal and produσes an Inσomin Line Aσtive Status Bit signal (STA 4) . As to the settin of hardware-busy flip flop 19A, this is σontrolled by th Inσoming Line Current Termination Strobe signal (STB 0) tha is produσed by one-shot 15C (FIG. 15) . As to the resettin of flip flop 19A, this is σontrolled by a signal produσe by an OR gate 19E. A prompt tone one-shot 19F produσes a Prompt Ton Control signal (CTL 49) on its Q output. This CTL 49 signa σontrols switσh 16J (FIG. 16) , and is one of the signal that, as shown in FIG. 17, is applied to OR gate 17E to rese audio connect flip flop 17C. The Q output of one-shot 19 produces a signal that triggers an end tone one-shot 19G. A Prompt Tone End Strobe signal (STB 4) is produced b one-shot 19G; it is one of the signals that is applied t OR gate 17D (FIG. 17) to provide for setting audio σonneσ flip flop 17C. The STB 4 signal is also applied to a se input of an inσoming line σonneσt flip flop 19H that produσe an Inσoming Line Conneσt Control signal (CTL 50) . The CT 50 signal σontrols hook-switch simulating switσh 15B (FIG. 15) . The reset input of flip flop 19H "~ reσeives a signa produσed by an OR gate 191. One of the signals applied t OR gate 191 is the Inσoming Line Current Termination Strobe signal (STB 0) , whiσh is produced by one-shot 15C (FIG. 15) . .Thus, when a caller hangs up, flip flop 19H is reset. In acσord with a partiσularly preferred feature, eaσh line σard is σontrolled to operate in traffiσ dependent modes, one of whiσh is referred to as a multi-mode and the other as a forward mode. While a line σard operates in the multi-mode, the attendant remains on line by keeping the multi-purpose station off-hook between inσoming σalls. To alert the attendant who is staying on line between σalls that another σall is ready to be extended to the attendant's multi-purpose station, the prompt tone is propagated out via the outgoing line before inter-σonneσ- tion switσh 14C is σlosed. While a line σard is operated in the forward mode, the line σard is σontrolled so as to disconneσt the multi-purpose station between incoming σalls and to re-establish the multi-purpose station as a network station as part of the sequenσe of operations for responding to an inσoming σall. A forward mode flip flop 19J produσes a signal tha is applied to a disable input of prompt tone one-shot 19F. An AND gate 19K produσes a signal that is applied to trigger input of prompt tone one-shot 19F. The signals applied to AND gate 19K are the Outgoing Line Curren Status Bit (STA 1) and the Inσoming Line Ring Deteσt signa (STA 3) is true. The STA 1 signal is produced by one sho 151 (FIG. 15) , and is true while a call σonneσtion path i σompleted at both ends between the system and the multi purpose station (i.e., the attendant is on line). The ST 3 signal is produσed by one-shot 15E (FIG. 15) , and beσome true when a ring signal is deteσted, thereby indiσating a inσoming σall needs serviσe. While forward mode flip flop 19J is in its set state, prompt tone flip flop 19F is disabled from responding t the signal applied to its trigger input. The set input o forward mode flip flop 19J is σonneσted to the output of gate 19L. The signal that gate 19L produσes is true whil the STA 1 signal is false and. the STA 3 signal is true. In addition to the role the STA 3 signal plays in disablin prompt tone one-shot 19J, the STA 3 signal is, as shown i FIG. 18, one of the signals applied to OR gate 18X. Whe the STA 3 signal is forσed true by deteσtion of the ringin signal, this sets outgoing line connect flip flop 1ST, an thereby initiates a timing sequence to call the attendant. While forward mode flip flop 19J is in its rese state, one-shot 19F is not disabled, and it responds to th trigger signal produσed by an AND gate 19K. When one shot 19F responds to the trigger signal, it produσes pulse in the Prompt Tone Control signal (CTL 49) . Thi causes switch 16J (FIG. 16) to close temporarily so tha the Prompt Tone Audio signal (AUD 3) propagates as th Outgoing Line Audio signal (AUD 0) . This also temporaril forces NOR gate 17K (FIG. 17) to produce a false logi level in the Outgoing Line Music Control signal to preven music from being propagated out over the outgoing line. With reference to FIG. 20, there will now be desσribe line σard σirσuitry for DTMF number generation and for in band signal decoding. This σircuitry forms part of th cirσuitry of functional block 141 (FIG. 14) , and include a decoder 20A, a DTMF generator 20B, and a DTMF reσeive 20C. DTMF generator 20B stores a seleσted telephone numbe used in placing a call to a multi-purpose station. DTM receiver 20C provides for receiving and decoding in-ban signals for security and other purposes. DTMF receive 20C receives the Outgoing Line Audio signal (AUD 0) , an produces a signal on a data valid output when it detect the presence of a touch tone pair constituting an in-ban signal. This output signal is applied to a gate 20D tha produces a DTMF Data Valid Control signal (CTL 35) t control an enable input of decoder 20A. Gate 20D als responds to an Internal DTMF Mute Control signal (CTL 33) that is produσed by an AND gate 20E. The CTL 33 signal is one of the signals provided to OR gate 17E (FIG. 17) to σause audio σonneσt flip flop 17C to reset. While the CTL 33 signal is false, and valid data is being produσed by reσeiver 20C, gate 20D enables deσoder 20A to deσode a four-bit parallel σoded signal produσed by reσeiver 20C. The individual signals forming this coded signal are a DTMF Bus Bit 3 signal (CTL 36) ; a DTMF Bus Bit 2 signal (CTL 37) ; a DTMF Bus Bit 1 signal (CTL 38) ; and a DTMF Bus Bit 0 signal (CTL 39) . Decoder 20A produces the following signals: a DTMF D Key Strobe (STB 5) ; a DTMF 1 Key Strobe (STB 6) ; a DTMF 2 Key Strobe (STB 7) ; a DTMF 3 Key Strobe (STB 8) ; a DTMF 8 Key Strobe (STB 9) ; a DTMF 9 Key Strobe (STB 10) ; a DTMF 0 Key Strobe (STB 11) ; AND a DTMF * Key Strobe (STB 12) . The "D" key is provided on some speσial 4-σolumn touσh tone keypads. The STB 5 signal relates to this key; it is provided for future expansion and is not used in system IA. The STB 6 strobe signal is one of the signals provided to OR gate 171 (FIG. 17) to σause message 3 flip flop 17H to set. The STB 7 strobe signal is one of the signals provided to OR gate 17E (FIG. 16) to σause audio σonneσt flip flop 17F to reset. The STB 8 strobe signal and the STB 10 signal are among the signals provided to OR gate 17D (FIG. 17) to σause audio σonneσt flip flop 17F to set. The STB 9 strobe signal is one of the signals provided to OR gate 18V (FIG. 18) to σause outgoing line σonneσt flip flop 1ST to reset. The STB 11 strobe signal is provided to numerous σirσuits. As to σirσuitry shown in FIG. 19, the STB 11 strobe signal is one of the signals provided to OR gate 191 (FIG. 19) to reset inσoming line flip flop 19H; it is provided to the reset input of forward mod flip flop 19J; and it is one of the signals provided to O gate 19E to reset hardware-busy flip flop 19A. As t σirσuitry shown in FIG. 18, the STB 11 strobe signal i applied to the clear input of activate timer 18N and t " the disable input of activate abort one-shot 180. As t cirσuitry shown in FIG. 17, the STB 11 strobe signal i one of the signals provided to OR gate 17J to cause messag 3 flip flop to reset. The cirσuitry shown in FIG. 20 further inσludes retriggerable one-shot 2OF that produσes an External DTM Mute Control signal (CTL 34) . One-shot 20F is clock trig gered under control of signals provided by the ESt outpu of receiver 20C and by a delay one-shot 20G. One-shot 2O is disabled from responding to cloσk triggering while th signal produσed by one-shot 20G is true. If, after th signal produσed by one-shot 20G returns false, the signa produσed by the ESt output of reσeiver 20C remains true then one-shot 2OF responds to the σloσk trigger to forσ the CTL 34 signal true. The CTL 34 signal is one of th signals provided to OR gate 17E to σause audio σonneσ flip flop 17C to reset. Such resetting of flip flop 17 is part of an operation to provide source discrimination More particularly, when a false-to-true transition ocσur in a signal produσed by DTMF reσeiver 20C, thereby indiσatin that an in-band signal is present in the AUD 0 signal, i is initially ambiguous whether the sourσe of this in-ban signal is a multi-purpose station or an originating station However, beσause of the operation of one-shots 20G and 2O in response to reσeiver 20C, and beσause of the resultin operation of resetting of audio σonneσt flip flop 17C inter-σonneσtion switch 14C opens. Continued detection o the in-band signal after switch 14C opens cannot be at tributed to an originating station. The cirσuitry shown in FIG. 20 further inσludes DTMF Test Mode flip flop 2OH, and an OR gate 201. The output of flip flop 2OH produσes a signal that is provide to AND gate 20E. AND gate 20E produσes the Internal Mut Control signal (CTL 33) , and σauses it to be true if both the signal it reσeives from flip flop 2OH and a signal it reσeives from a Mute output of generator 2OB are true. The dialing tone-pair signals produσed by DTMF generator 2OB for the purpose of plaσing a σall to a multi-purpose station via an outgoing line σannot inadvertently be propagated out via an incoming line. This is so because the CTL 33 signal, when true, causes audio conneσt flip flop 17C to reset, thereby opening inter-σonneσtion switσh 14C. One of the advantageous features resulting from the in-band signal deσoding is that an attendant can cause an inσoming σall to be disσonnected while the attendant remains on line to the system. When the attendant taps the "0" key on the touch tone pad, the resulting in-band signal is deσoded by DTMF reσeiver 20C and deσoder 20A to forσe the STB 11 signal true. This σauses flip flop 19H (FIG. 19) to reset, whiσh in turn σauses inσoming line hook switσh 15B to open so as to disσonneσt the inσoming σall. With referenσe to FIG. 21, there will now be desσribed command-decoding circuitry of a line card. This σommand- deσoding σirσuitry inσludes four deσoder σirσuits 21A, 2IB, 21C, and 2ID, eaσh of whiσh is enabled by a pair of enabling signals to deσode Bits 0-3 of the σommand word received via the command word bus portion of the row bus for the row in which the line card is used. One of the enabling signals is produσed by a Sσhmitt trigger drive cirσuit 21E that responds to the Card Select signal. The cirσuitry shown in FIG. 21 further inσludes three Sσhmitt trigger driver σirσuits 2IF, 21G, and 21H, and a σapaσitor 211. Cirσuit 2IF provides buffering o the σloσk signal for the line σard; its output signal i the CK signal (CTL 32) . Cirσuit 21G provides buffering o the Message 2 Start/Stop strobe signal for the line σard; its output signal is the Message 2 Start/Stop Strobe signa (STB 13) . Cirσuit 21H provides buffering of the Prompt Ton signal for the line card, and capaσitor 211 provides DC isolation for the Prompt Tone signal (AUD 3) . With reference to FIG. 22, there will now be described cirσuitry for providing status data from the line σard to the row bus. This σircuitry includes a four-bit latσh and tri-state bus driver 22A, a tri-state bus driver and multi¬ plexer 22B, and a gate 22C. Driver 22A and multiplexer 22B are arranged and operate in almost the same way as latσh 7U and multiplexer 7T (FIG. 7) are arranged and operate to provide status data from monitor σard 3F. Multiplexer 22B has an "A Enable" σontrol input and a "B Enable" σontrol input that reσeive, respeσtively, a Status A Control signal (CTL 22) and a Status B Control signal (CTL 4) . These σontrol signals are produσed by deσoders 21C and 21A (FIG. 21) in response to digitally σoded σommands issued by controlling computer 3C, as explained more fully below. There will now be described the manner in which the above-described cirσuitry of a line σard responds to various digitally σoded σommands issued by σontrolling σomputer 3C. As stated above, eaσh suσh digitally σoded σommand has a two byte format, one byte for addressing a σard, and another byte defining a Command Word. Controlling σomputer 3C sends digitally σoded σommands in serial form to UART 6A in σommuniσations σard 3B. The Command Word is latσhed into latσh 6E, applied to the system bus, and applied to every row bus by its corresponding bus ' controller. The addressing byte is latched into latch 6D, then decoded to select a row and a line card within a row, with the result that a Card Select signal (FIGS. 5 and 21) for the addressed line card will be forced true. Driver 21E (FIG. 21) of the addressed line card enables deσoders 21A - 2ID to deσode the Command Word reσeived from the row bus. Eaσh of deσoders 21A - 21D has eight outputs, some of whiσh provide spares for system expansion. As to the outputs of deσoder 21A that are used in system IA, one of these produces a Message 4 On Control signal (CTL 0) . When controlling computer 3C issues a digital σommand to forσe the CTL 0 signal true, this results in setting message 4 flip flop 17F. Depending upon the position of option switσh 17G, this results in either the Outgoing Line Message 4 Control signal (CTL 45) or the Inσoming Line Message 4 Control signal (CTL 46) being forced true. If the CTL 45 signal is true, then switch 16F closes, so that the Message 4 Audio signal is gated through to the outgoing line. If the CTL 46 signal is true, then switch 16A closes, so that the Message 4 Audio signal is gated through to the inσoming line. On another one of its outputs, deσoder 21A produσes a Message 4 Off Control signal (CTL 1) . When σontrolling σomputer 3C issues a digital command to force the CTL 1 signal true, this results in resetting message 4 flip flop 17F. Depending upon the position of option switσh 17G, this results in either the Outgoing Line Message 4 Control signal (CTL 45) or the Inσoming Line Message 4 Control signal (CTL 46) being forσed false. Whenever the CTL 45 signal is false, switσh 16F is open, so that the Message 4 Audio will not propagate to the outgoing line. Whenever the CTL 46 signal is false, switσh 16A is open, so that the Message 4 Audio signal will not propagate to the inσoming line. On another one of its outputs, deσoder 21A produσes a DTMF Test Mode On Control signal (CTL 2) . When σontrolling σomputer 3C issues a digitally σoded command to force the CTL 2 signal true, this results in setting the DTMF Test Mode flip flop 20H. On another one of its outputs, deσoder 21A produσes a DTMF Test Mode Off Control signal (CTL 3) . When σontrolling σomputer 3C issues a digitally σoded σomman to forσe the CTL 3 signal true, this results in resettin DTMF Test Mode flip flop 20H. On another one of its outputs, deσoder 21A produσe a Status B Control signal (CTL 4) . The σirσuitry tha responds to this σontrol signal also responds to a Statu A Control signal (CTL 22) produσed by deσoder 21C. Whe σontrolling σomputer 3C issues a digitally σoded σomman to obtain Status A data from an addressed line σard, deσode 21C forσes the Status A Control signal (CTL 22) true. I response, multiplexer 22B propagates, signals from its "A" data inputs to Bits 4-7 of. the Status Bus. Its "A" input inσlude Ground Return, i.e., a false logiσ value; th Inσoming Line Current status Bit signal (STA 2) ; the Outgoin Line Conneσt Control signal (CTL 55) ; and the Inσomin Line Busy Control signal (CTL 48) . When σontrolling σompute 3C issues a digitally σoded σommand to obtain Status data from an addressed line card, decoder 21A forces th Status B Control signal (CTL 4) true. In response, multi¬ plexer 22B propagates signals from its "B" data inputs to Bits 4-7 of the Status Bus. Its "B" inputs include Ground Return; the Outgoing Line Current status Bit signal (ST 1) ; the On-Hook Timer Status Bit signal (STA 5) ; and the Monitor Status Bit signal (STA 6) . As for Bits 0-3 of a status word provided by a addressed line card, latch 22A has an enable input tha responds to the- Status A Control signal (CTL 22) . Whe controlling ' σomputer 3C issues a digitally σoded σomman to obtain Status A data from monitor σard 3F, deσoder 21 forσes the Status A Control signal (CTL 22) true. I response, latσh 22A propagates signals from its data input to Bits 0-3 of the Status Bus. Its data inputs are th four parallel output signals of reσeiver 20A, i.e., th CTL 36, CTL 37, CTL 38, and CTL 39 signals. Latσh 22 σopies these signals whenever the output signal of gat 22C is forced true by the DTMF Data Valid Control signa (CTL 35) being true while the Status A Control signal (CT 22) is false. On another one of its outputs, decoder 21A produces a Hardware Un-Busy Control signal (CTL 5) . Some of the line card σircuitry that is σontrolled by this σontrol signal is also σontrolled by an Un-Busy Inσoming Line Control signal (CTL 11) produσed by deσoder 2IB. In fact, one command of the σommand repertory forσes each of the CTL 5 and CTL 11 signals true. This command is issued to change the mode of the line card to the call forward mode when the line card is in an idle condition. When the CTL 5 signal is forced true, this ensures that incoming line hardware busy flip flop 19A is in its reset state. This is a necessary but not a sufficient condition to cause ground start simulating switch 15A to be open. With the CTL 11 signal forced true, this ensures that incoming line software busy flip flop 19C is in its reset state. With- eaσh of flip flops 19A and 19C in their reset state, the CTL 48 signal must be false, thereby ensuring that ground start simulating switch 15A is open. As to other outputs of decoder 2IB that are used in system IA, one of these produσes a System Initialize Control signal (CTL 8) that performs the same resetting funσtion for a line σard that the CTL 56 signal performs for monitor σard 3F. Another one of the outputs of deσoder 2IB is an Outgoing Line Off Hook & Dial Control signal (CTL 9) . When controlling computer 3C issues a digitally coded command to force the CTL 9 signal true, this results in setting off- hook flip flop 18R, which remains in its set state until completion of execution of operations required by this command. While flip flop 18R is set, the signal its Q output produces is false. This is a necessary condition for the signal produced by NOR gate 18Y to be true. The other neσessary σonditions are that three other signals must also be false. These three signals are the Inσomin Line Current Status Bit signal (STA 2) , the Outgoing Lin Current Status Bit signal (STA 1) , and the On-Hook Timer Status Bit signal (STA 5) . r The STA 2 signal being false indicates that no call is in progress on the incoming line. The STA 1 signal being false indicates that no call is in progress on the outgoing line.- ^ The STA 5 signal being false indicates that a minimum threshold time period has passed since outgoing hook-switch 15F opened, thereby providing a basis for distinguishing a hook-switch flash within a single call from the termination of one call and the start of another. When all these necessary conditions prevail, the signal produced by NOR gate 18Y forces OR gate 18U to set Outgoing Line Connect flip flop 18T. In response, OR gate 181 forces the CTL 55 signal to be true, and this signal causes outgoing line hook-switch 15F to close, thereby simulating an off-hook telephone. Also, the false-to-true transition in the signal produced by the Q output of flip flop 18T triggers dial tone one-shot 18K. As a result, a pulse is defined in the signal produced by one-shot 18K. This signal has multiple funσtions, and is referred to as the Outgoing Line Ground Control (CTL 51) signal because it controls outgoing line ground-start switch 15G, and is also referred to as the Redial Preset Strobe signal (STB 3) because it controls the memory strobe input of DTMF generator 20B. In particular, it prepares generator 20B to initiate dialing upon receipt of an ensuing input of parallel signals representing the "#" symbol. The pulse in the CTL 51 signal temporarily closes outgoing line ground-start switch 15G for approximately one-half second to stimulate generation of dial tone. The pulse in the STB 3 signal forces OR gate 17E to reset audio connect flip flop 17C. This ensures that the Audio Connect Control signal (CTL 44) is false, and thereby ensures that inter-conneσtion switch 14C is open while a call is being placed via the outgoing line. At the end of thispulse, its true-to-false transition triggers delay one-shot 18L to allow sufficient time to ensure that dial tone is provided. At the end of the approximately one-second long delay defined by one-shot 18L, a true-to-false transition in the signal it produces triggers dial one-shot 18M. The signal one-shot 18Mproduces is a DTMF Dial Control signal (CTL 52) . It is coupled through diodes to the 4 and C_ inputs of generator 2OB. These inputs in combination correspond to the "#" symbol; the parallel signals coupled through the diodes initiate the dialing, which is completed before the end of the ap¬ proximately two-second long delay provided by one-shot 18M. The true-to-false transition in the CTL 52 signal also triggers activate timer 18N to initiate its timing interval of up to a maximum of 30 seconds. The signal produced by the Q output of activate timer 18N is the Message 1 Control signal (CTL 53) that controls switch 161. While the CTL 53 signal is true, switch 161 is closed, and the Message 1 Audio signal (AUD 6) is applied to the outgoing line. The CTL 53 signal is also applied to the trigger inputs of timer end one-shot 18G and activate abort one-shot 180c The true-to-falsβ transition in the CTL 53 signal always triggers (regardless of whether it occurs at the end of the maximum time-out period of 30 seconds or before) timer end one-shot 18G. Thus, a true pulse is defined in the Activate Timer End Strobe signal (STB 1) in either case. On the other hand, the true-to-false transition in the CTL 53 signal triggers activate abort one-shot 180 only if the STB 11 signal has remained false throughout the full 30 seconds, and according¬ ly has not disabled activate abort one-shot 180. On another one of its outputs, decoder 2IB produces an Outgoing Line On Hook Control signal (CTL 10) . This signal sets flip flop 18S, which remains in its set state until completion of execution of operations required by this command. With respect to this σommand, σonsider a situation prevailing at the end of a shift. If any attendant from the shift is σontinuing to • σonfer with an inσoming σaller, it is desirable to await the end of that σonversation before terminating the σall σonneσtion path to that atten¬ dant. When the σall in progress at the time of issuanσe of this σommand ends, the STA 2 signal beσomes false. Then, beσause flip flop 18S is set (therefore the signal produσed by its Q output is false) , and the STA 2 signal is false, NOR gate 18W produces a true signal, causing OR gate 18V to reset outgoing line connect flip flop 18T. This starts the sequence involved in disconneσting the call conneσtion path to the attendant. This sequence entails playing message 2 within the overall time alloted by disconneσt timer 18H, and, finally, . when the CTL 55 signal beσomes false at the end of message 2, it causes hook-switch simulating switch 15F to simulate an on-hook condition. The triggering of disconnect timer 18H enables message 2 flip flop 18J to be toggled by the next ensuing false-to-true transition in the Message 2 Start/Stop Strobe signal (STB 13), which is produced by driver cirσuit 21G. The signal produced by message 2 flip flop 18J is the Message 2 Control signal (CTL 54) . While the CTL 54 signal is true, switch 16H is closed and propagates the Message 2 Audio signal (AUD 7) as the Outgoing Line Audio signal (AUD 0) . The next false-to-true transition in the STB 13 signal causes AND gate 18P to clear disconneσt timer 18H and simultaneously toggles message 2 flip flop 18J. On another one of its outputs, deσoder 21B produσes a Busy Incoming Line Control signal (CTL 12) . Controlling computer 3C issues this command to exercise software σontrol over the incoming line; more particularly, when this command- is decoded, incoming line software busy flip flop 19C is set. While flip flop 19C is set, the CTL 48 signal produced by OR gate 19B must be true, and aσσordingly ground start simulating switσh 15A must be σlosed. Controlling σomputer 3C exerσises this software control as part of a software sequence for loading a phone number and placing a call to the multi-purpose station identified by that phone number. As part of this software sequenσe, σontrolling σomputer 3C issues a σommand to σause deσoder 2ID to forσe the Phone Number Memory Strobe Control signal (CTL 30) true. While true, the CTL 30 signal forσes OR gate 201 to provide a memory strobe to DTMF generator 20B. Further as part of this software sequenσe, controlling computer 3C issues a series of commands to load a phone number. Eaσh of the commands in this series σauses eaσh of deσoders 21C and 21D to forσe true one of the signals it produσes. For example, to load the digit "9," controlling computer 3C issues a command to force both the DTMF Number Dial R3 Control signal (CTL 18) and the DTMF Number Dial C3 Control signal (CTL 26) true. More generally, to load any digit, controlling computer 3C issues a command to cause decoders 21C and 21D to force one of the CTL 16, CTL 17, CTL 18, and CTL 19 signals true, and one of the CTL 24, CTL 25, CTL 26, and CTL 27 signals true. After issuing this series of commands to load the series of digits of the phone number into DTMF generator 20B, controlling computer 3C issues the command that causes decoder 2IB to initiate the off-hook and dial sequence that begins with the CTL 9 signal becoming true. Controlling computer 3C relentlessly monitors the status of each line card by issuing commands to retrieve status A and status B words. This relentless monitoring is a process that is independent of, and in parallel with, the above-described sequence of operation. Based on the retrieved status data, controlling computer 3C communiσates via modem phone line 3E with supervisory σomputer 3D to provide data used to update the displayed status report. For example, when σontrolling computer 3C finds that transition has ocσurred from one of three signals being true, that one being the CTL 48 signal, to all three signals being true, the three being the CTL 48, CTL 55, and STA 1 signals, then σontrolling σomputer 3C sends data to super- visory σomputer 3D to σause the σolor for the σorresponding line σard to σhange from blue to magenta. Further as part of this independent and parallel proσess, σontrolling σomputer 3C reσognizes the oσσurrenσe of the enσoded seσurity-σlearanσe signal (i.e.., the parallel bits of CTL 36 - CTL 39) . After this is reσognized, σon¬ trolling computer 3C issues the command to cause the CTL 11 signal true. This resets flip flop 19C. As to the matter of retries, σontrolling σomputer 3C monitors the STA 1 and the CTL 55 signals. If transitions occur in these signals (from true to false) , then controlling computer 3C inσrements its σount of tries, and, if the inσremented σount is less than a pre-set number, initiates another try to σomplete a σall ' with an attendant. On others of its outputs, deσoder 21B produces an Outgoing Line Fast Disconneσt Control signal (CTL 13), and an Outgoing Line Fast Conneσt Control signal (CTL 14) . With respeσt to these deσoded σommands, σonsider a sequence of operations carried out under software control to transfer a call from one attendant to another. At the outset of suσh a transfer, there is already a σall in progress. Aσcording- ly, the following signals are true: the STA 1 signal and the CTL 55 signal (in combination, this indicates a call conneσtion path is σomplete on the outgoing line) ; and the STA 2 signal (this indicates a call connection path is complete on the incoming line) . Under these conditions, σontrolling σomputer 3C issues a σommand to monitor the inσoming line by causing decoders 21C and 21D to force the CTL 21 and CTL 28 signals true. The CTL 21 signal, while true, resets monitor side flip flop 17B (FIG. 17). The CTL 28 signal, while true. sets monitor flip flop 17A (FIG. 17) ' . Next, σontrolling computer 3C issues a command to σause deσoder 21A to forσe the CTL 2 signal true. This sets flip flop 2OH and this in turn disables the internal mute so as to allow DTMF deσoder 20A to deσode internally generated DTMF signals. Having established this σondition, σontrolling σomputer 3C issues a σommand to σause decoders 21C and 2ID to force the CTL 16- and CTL 25 signals true so as to simulate a digit "2" at the input of DTMF generator 2OB. In response, DTMF generator 2OB produces a DTMF signal corresponding to the digit "2." This DTMF signal is reσeived via reσeiver 20C, and is decoded by decoder 20A so that the STB 7 signal becomes true. The STB 7 signal causes OR gate 17E to reset audio connect flip flop 17C, thereby opening inter- connection switσh 14C. At this .point, the supervisor can confer with the incoming caller, and the attendant on the outgoing line has been isolated from the incoming line. Having established this condition, controlling computer 3C issues a σommand to cause decoder 21B to force the CTL 13 signal true. This causes OR gate 18V to reset outgoing line connect flip flop 1ST. This in turn causes disconnect timer 18H to initiate the sequence of operations described above for playing message 2 and then disσonneσting the σall σonnection path to the attendant. Controlling computer 3C monitors status data, as desσribed above, to determine that the disσonneσtion has oσσurred and that suffiσient time has passed to go off hook and dial. This determination is based on monitoring three signals: the on-hook timer status signal (STA 5) ; the STA 1 signal; and the CTL 55 signal. When all three of these signals have beσome false, σontrolling computer 3C proceeds to download a phone number by the series of σommands desσribed above. This downloaded .phone number identifies the telephone of a transferee attendant. Next, σontrolling σomputer 3C issues a σommand to σause deσoder 2IB to forσe the Outgoing Line Fast Conneσt Control signal (CTL 14) true. While true, the CTL 14 signal σauses OR gates 18X and 18U to set flip flop 18T. This initiates the hardware sequenσe of plaσing the σall to the transferee attendant. Simultaneously, the CTL 14 signal σauses OR gate 171 to set message 3 flip flop 17H to forσe the CTL 47 signal true. This disables aσtivate timer 18N. Thus, although the sequential operation of one-shots 18K, 18L, and 18M is the same as desσribed above, aσtivate timer 18N does not respond to triggering in this transfer sequenσe. As a result, the messag ' e 1 σontrol signal (CTL 53) remains false; further, neither one-shot 18G nor one-shot 180 is triggered. Whenthe security-verification signal for a transferee attendant is received, the STB 10 signal is forced true, and this σauses OR gate 17J to reset flip flop 17H. As a result, the CTL 47 signal returns to its normal false value. Simul¬ taneously, the STB 10 signal σauses AND gate 17D to set audio σonneσt flip flop 17C. Thus, at the end of this transfer sequenσe, the call on the incoming line is conneσted through inter-σonneσtion switσh 14C to the outgoing line σonneσted to the transferee's multi-purpose station, and the monitor audio is σonneσted to the inσoming line. To σonneσt the monitor audio to the outgoing line, controlling computer 3C issues a command to forσe the CTL 20 signal true. This sets monitor side flip flop 17B. Deσoder 21D also produσes aMonitor Off Control signal (CTL 29) in response to a digitally σoded σommand issued by σontrolling σomputer 3C. The CTL 29 signal has two functions. One of these functions is to reset monitor flip flop 17A. While monitor flip flop 17A is in its reset state, AND gates 17L and 17M force the CTL 41 and CTL 42 signals false, so that both switch 16C and switch 16D are open, whereby neither the incoming line to the partiσular line σard, nor the outgoing line from the par¬ tiσular line σard is σonneσted to supervisory station II. The seσond funσtion of the CTL 29 signal is to σause OR gate 17D to set audio σonnect flip flop 17C. This function is involved when a supervisor has completed a conversation with an incoming caller while inter-conneσtion switσh 14C is open. When the Monitor Off Control signal is reσeived, it forσes inter-σonnection switch 14C to close, so that the incoming caller can resume conferring with an attendant. There will now be described, with referenσe to FIGS. 24 to 28, other representative human-readable status reports that are displayed to the supervisor on the sσreen of video display terminal IF. The ensuing desσription of these displayed status reports brings outhowthe supervisor is prompted to use either mouse IG alone, or mouse IG and keyboard IH, in interaσtively performing a series of steps to effeσt a seleσtion and every sub-seleσtion needed to enter a supervisory σommand. In FIG. 24, the triangular-shaped mouse σursor appears in the main menu seleσtion line, next to the "Change" menu item. The supervisor has selected this item on the main menu seleσtion line by moving mouse IG to position the mouse cursor next to the "Change" item and cliσking the button on the mouse. As one result of this seleσtion, the "Change" item is highlighted to indiσate that it has been seleσted; the highlighting is indiσated in FIG. 24 by a single-line box surrounding the "Change" item. As another suσh result, there appears in FIG. 24 a pull¬ down menu, whiσh is associated with this selected main menu item and which is surrounded by a double-line box. This pull-down menu presents the following six sub-selec¬ tions: "Call"; "Disconneσt"; "Busy WATS"; "Unbusy WATS"; "Initialize"; and "Configure." The presentation of these six sub-seleσtions prompts the supervisor to proσeed to a step to select one of these six sub-selections by ap- propriately positioning the mouse cursor, and then σliσking the mouse button. FIG. 25 shows the top of the displayed status report after the supervisor has seleσted the "Call" sub-seleσtion. As one result of this seleσtion, the "Call" sub-selection is highlighted; this is indicated in FIG. 25 by a single- line box surrounding the "Call" sub-selection. As another such result, there appears in FIG. 25 a pull-out menu, whiσh is assoσiated with the "Call" sub-seleσtion and whiσh is surrounded by a single-line box. This pull-out menu presents the following four options: "All"; "Random"; "Line 77"; and "Canσel." The presentation of these four options prompts the supervisor to proσeed to a step to seleσt one of these options. By seleσting the "All" option, the supervisor σompletes the steps of entering a supervisory σommand to cause every line card to execute the sequence of operations, under control of controlling computer 3C, involved in placing a call to an attendant who will answer and service calls via the respective line card. The "Random" option enables the supervisor to position the mouse cursor to any arbitrary one of the matrix of 105 line card representing elements, click the mouse button and thereby identify that line card for use in placing a call to an attendant. By doing so, the supervisor completes the steps for entering a supervisory command appliσable to the identified line σard. If the supervisor wants to enter a supervisory σommand appliσable to another line σard, this σan be done again in the same way without repeating all the steps starting from seleσting "Call" from the main menu seleσtion line. As to the "Line 77" option, line σard 77 happens to be the current line card. That is, it is the line card σorresponding to the box framed by the display pointer (FIG. 23) at the time the supervisor seleσted the "Call" item on the main menu. Any line σard σan similarly be the σurrent line card and be so indicated as part of this pull-out menu. In any case, the seleσtion of this option σompletes the steps for entering a supervisory σommand to σause the σurrent line σard to exeσute the sequenσe of operations involved in plaσing a σall to an attendant. The "Canσel" option is σhosen if for example the supervisor had erron¬ eously seleσted the "Call" sub-seleσtion or the "Change" item. It is also σhosen when the supervisor has entered the last of a series of σommands from the random seleσtion. The pull-out menu that appears to the right of the "Call" sub-seleσtion in FIG. 25 will also appear to the right of eaσh of four other seleσted sub-seleσtions within the pull-down menu. Thus, the supervisor σan σhoose to disσonneσt every attendant, eaσh of a series of individually identified attendants, or the attendant serviσing the line card such as line card 77 that is the currently selected line card. The same is true for causing the busying or un-busying of the incoming lines to the line cards, and for initializing the line σards. As to the "Configure" sub-seleσtion, this has an assoσiated sub¬ menu (not separately shown) for prompting the supervisor to complete the steps involved in entering a σhange con¬ figuration command. The options of this sub-menu are to change parameters that are global to the system, so there is no need for an additional pull-out menu to prompt for line card identification. These global or system level parameters inσlude ringthrough time, ringthrough length, number of retries, and an emergenσy telephone number. A ringthrough is a period during the day for whiσh it is projeσted that inσoming traffiσ will be relatively high so that it is desirable to have attendants on line and ready to answer and serviσe inσoming σalls immediately. For some appliσations of system IA, it will be the σase that inσoming traffiσ volume will vary in a somewhat σyσlical basis during the day: that is, there will be a period of low-volume incoming traffiα; followed by periods in whiσh inσoming traffiσ rises rapidly, then remains high for awhile, then triσkles down to a low .volume; then the σyσle will repeat again albeit not neσessarily with a fixed period. Although variable, the inσoming traffiσ σan generally be prediσted within reasonable limits. Aσσordingly, the projeσted ringthrough times σan be stored in reσords on disk and loaded into supervisory σomputer 3D. For eaσh projeσted ringthrough, these reσords speσify a real time used in determining when to start a ring- through, and an interval used in determining when to end the ringthrough. The supervisor σan issue a supervisory σommand to override any projeσted value. FIG. 26 is somewhat similar to FIG. 23 in that it shows an entire representative displayed status report. In the displayed status report of FIG. 26, the boxes rep¬ resenting the line σards are shaded to indiσate- various σolors representing different status σonditions for dif¬ ferent line cards. Further, FIG. 26 shows a pull-down menu that is associated with the "Info" item of the main menu line. This pull-down menu is surrounded by a double- line box and presents information about the current line card, which happens to be line σard 77 in this example. The information inσludes the name of the attendant σurrently designated to answer and serviσe inσoming σalls through this line σard; that attendant's phone number and status and activity and statistical data as to number of calls handled and calls dropped. As to the displayed status field, this can be, in addition to "Absent," as shown in FIG. 26, either "Refused" or "Transferred" or "Cancelled." As to the displayed activity field, this is either "Yes" or "No." 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. This prompt appears as a result of the supervisor having first σliσked on "Phone," and having then entered a phone number by keyboard entry. Through use of this feature, an attendant who had been sσheduled to answer and serviσe σalls from one multi-purpose station, for example at home, can answer and service calls from another station, for example, the phone at the home of someone the attendant is visiting that day. ~~ 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 "Shift" ' from the main menu selection line. In this pull-down menu, the sub-selections available are: "Load Shift Disk"; "Cancel Operator"; and "Cancel Aux Operator." The shift disk is a conventional floppy disk, pre-recorded with all necessary data for a series of shifts for a week. This data include name, phone number, and a Boolean field indicating the attendant either to be a primary attendant assigned to a particular line card or to be an auxiliary attendant to be in a pool available to be called if the need arises. The above-described displayed status reports are generated by supervisory computer 3D under program control, based in part on status data provided to supervisory computer 3D from controlling σomputer 3C. As stated above, in the presently preferred embodiment, eaσh of supervisory σomputer 3D and σontrolling σomputer 3C is a personal σomputer. Eaσh uses a σonventional disk operating system for performing a variety of low level funσtions under control of an application program. The application programs for supervisory computer 3D and controlling computer 3C may be written in any of numerous suitable languages. It is preferred that a σompiled program rather than an interpretive program be used, for speed of exeσu- tion, partiσularly with respeσt to matters suσh as rewriting the sσreen. A σompiled program written in PASCAL has ample speed for this application. With reference to the flow σharts of FIGS. 29-34, there will now be desσribed the internal operations of supervisory σomputer 3D. Three main proσesses are σarried out on an independent and essentially parallel basis by supervisory σomputer 3D under program σontrol. To this end, the programming of supervisory computer 3D uses non- preemptive multi-tasking techniques to aσhieve the effeσt of timesharing among these, three proσesses. The flow σhart of FIG. 29 depiσts the major operations of one of these three proσesses, whiσh σonσerns σommuni¬ σations between supervisory σomputer 3D and σontrolling σomputer 3C. It will be reσalled that eaσh of supervisory σomputer 3D and σontrolling σomputer 3C has a modem, and the two modems are interσonneσted by modem phone line 3E. Suitably, data are transferred between these two σomputers in paσkets. Eaσh suσh paσket has a standard header format, preσeding a variable length reσord. In aσσord with standard teσhniques, the header inσludes bytes for a σheσk sum and for the length of the ensuing variable length reσord. Various and sundry detailed operations are involved in assembling suσh paσkets, in establishing σommuniσation parameters for the modems, and in serially providing bytes to the modems. Providing for these and similar detailed operations are routine matters and are subordinate to the broader matters covered in FIG. 29 and the remaining flow charts. The following PASCAL-language declarations set out constants that, in the application program for supervisory computer 3D, are referred to in operations to communiσate supervisory σommands from supervisory σomputer 3D to σontrolling σomputer 3C: { Communications-related packets. } Const COMM_PREFIX $80; {High 4-bits of a σomm command. ACK_CMD $81; {Aσknowledge packet receipt. NAK CMD $82; {Error in packet σommuniσations { Telephone number paσkets.} Const TELENUM_PREFIX $90; {High 4-bits of telenum command GET__TELENUM_CMD $90; {Get phone number Controller. SET_TELENUM_CMD $91;. {Set number in Controller. BLOCK TELENUM CMD $98; {Set numbers for a row. { The line σontrolling σommands.} Const ALL_LINES = $7Fj {For commands on all lines. LINECTRL_PREFIX = $A0; {High 4-bits of line- cont. σmd. CALL_OPER_CMD = $A0, {Call operator(s) . DISCONN_OPER_CMD = $A2, {Disσonneσt operator(s) . BUSY_CALLER_CMD = $A3, {Make σaller side(s>-busy. UNBUSY_CALLER_CMD = $A4 {Make σaller side(s) unbusy. INIT CARD CMD = $A5] {Initialize line σard(s) . { Monitor-related σommands. } Const MONITOR_PREFIX - $B0; {High 4-bits of monitor command MONITOR__CALLER_CMD = $B0; {Monitor the caller side. MONITOR_OPER_CMD - $B1; {Monitor operator side. { Parameter-changing commands. } Const PARAM_PREFIX = $C0 {High 4-bits of parameter cmd. SET_RETRY_CMD = $C0 {Set dialing retry σount. SET_EMER_NUM_CMD = $C1 {Set emergenσy transfer number. SET_NPA_CMD = $C2 {Set the loσal area σode. SET_LOCAL_ACS_CMD = $C3 {Set the loσal aσσess numbers. GET_READY_CMD = $C8 {Get dialing retry σount. GET_EMER_NUM_CMD ' » $C9 {Get emergenσy transfer number. GET_NPA_CMD = $CA {Get the local area code. GET LOCAL ACS CMD - $CB {Get the local access numbers. { Emergency and help servicing commands.} Const EMERHELP_PREFIX = $D0; {High 4-bits of emer/help cmd. TRANSFER_EMER_CMD = $D0; {Transfer caller to emer numbe HELP_SERVICED_CMD = $D1; {Signal the help as serviσed. EMER SERVICED CMD = $D2; {Signal the emer as serviσed. { For the status. } {High 4-bits of status/dump σmd. {Returned status σommand. {Dump up to 105 new statuses. {Update the supervisor. {Poll the C. Comp. for paσkets. (The term "operator," as used in the σo ments, means t attendant.) In bloσk 29A of FIG. 29, supervisory σomputer 3D determines whether any supervisory σommand is to be sent to σontrolling σomputer 3C. Bloσk 29A is in aσσord with a σonvention used throughout the flow σharts in whiσh a diamond-shaped bloσk indiσates a control structure for controlling the flow of operations. A corresponding programming control structure is an "if-then-else" control structure. As to supervisory commands, the programming of supervisory σomputer 3D inσludes σonventional mouse driver programming and assoσiated programming that provides for determining when and whiσh supervisory σommand has been entered by the supervisor. Further, conventional circular queue managing programming is included to provide a list of entered supervisory commands and to provide head and tail pointers to the list. If the tail pointer exceeds the head pointer by more than one (modulo the number of σells provided by the σirσular queue) then there are supervisory σommands waiting in the queue to be sent to σontrolling σomputer 3C. If there is a supervisory σommand to send, the flow proσeeds to bloσk 29B in whiσh supervisory σomputer 3D sends a supervisory σommand to σontrolling σomputer 3C and waits for either an "aσknowledge" or a "no aσknow- ledge." In bloσk 29C, supervisory σomputer 3D determines whether a "no aσknowledge" has been returned and, if so, re-enters bloσk 29B. Otherwise, the flow proσeeds to a bloσk 29D, whiσh entails moving in the σirσular queue to the next supervisory σommand to send, and then looping baσk to re-enter bloσk 29A. If within bloσk 29A it is determined that there is no supervisory σommand to send, the flow proσeeds to bloσk 29E in whiσh supervisory σomputer 3D determines whether to poll for status data. The following PASCAL-language deσlarations set out σonstants that, in the appliσation program for supervisory σomputer 3D, are referred to in operations to reσeive status data from σontrolling σomputer 3C: { Status byte returned from the σontrolling σomputer 3C.} { Low nibble σonσerns sσreen σolors. } Const S_DIALING = l; { Card is trying to reaσh an operator. } S UNREADY = 2; { Operator is not ready for inσoming calls.} S_READY 3; { Operator is ready and waiting for calls. } S_CIP = 4; { There is a call in progress on the line.} S_BUSY = 5; { The caller side of the line is busied. } S_UNBUSY = 6; { The caller side of the line is un- busied. } S_FWD = 7; { The card is in forward mode. } S_UNKN0WN = 8; { The card is in unknown condition. } S NOCARD = 9; { There is no σard inthe givenposition. } { High nibble σonσerns other status matters. } Const S_EMER 16; { An emergenσy request for the given line.} S_HELP 32; { A help request for the given line. } S_CANCEL = 48; { The help or emer request is σanσelled. } S EFERRED = 64; { The emergency call has been trans¬ ferred. } S_N00PER = 80; { The oper. didn't respond in retry limit. } S REFUSED = 96; { The operator refused further σalls. } If no suσh polling is to be σonduσted, the flow returns to bloσk 29A. Otherwise, the flow proσeeds to bloσk 29F in whiσh supervisory σomputer 3D gets a status paσket or an aσknowledge paσket from σontrolling σomputer 3C. Next, the flow proσeeds to bloσk 29G, in whiσh super¬ visory σomputer 3D determines whether a status paσket has been reσeived. If not, the flow returns to bloσk 29A. Otherwise, the flow proσeeds to bloσk 29H, in whiσh super¬ visory σomputer 3D updates the displayed status report in aσσord with the data provided by σontrolling σomputer 3C in the reσeived status paσket. In the presently preferr¬ ed embodiment, the σolors of the boxes are ' σontrolled by sσreen attribute bytes stored in the sσreen buffer. The following PASCAL-language σonstant deσlarations apply to these attribute bytes: { The colors of the line card status } Const Light magenta/black Light red/blaσk Yellow/blaσk Green/blaσk Light blue/blaσk Brown/blaσk Grey/blaσk Black/black Makes a σolor flash Thus, there is no need to keep a separate table in supervisory σomputer 3D of status data, by line σard, with respect to status matters such as dialing or not, ready or not, and the like. Next, the flow proceeds to block 291, in which supervisory computer 3D makes appropriate changes in emergency and help queues, these being first- in, first-out variable length lists kept in memory. Next, controlling σomputer 3D in block 29J makes appro¬ priate changes to a database it maintains for statistical purposes. This database comprises records in which are kept various statistics such as number of calls, number of dropped calls and the like. The following PASCAL- language type declaration applies to each database reσord in supervisory σomputer 3D: Type OpStat_Type = array[l..105] of reσord op_σalls, { σalls per ringthrough op_drops, { drops per ringthrough last_stat, { last status, reσorded for later σomparis in σomputing length of σall oper_sσnd, { time of reσeipt of last status-seσs oper_time, { time of reσeipt of last status-hrs/mins oper_dofw { time of reσeipt of last status-day of wk. n : Integer; u end; The operations depiσted in FIG.29B relate to automatiσ features for originating σalls to auxiliary operators when the need arises to do so. As stated above, data are 5 pre-reσorded on a shift disk to provide the names, phone numbers, and other information concerning persons who have been scheduled to serve as either ' primary attendants or in a pool of auxiliary attendants. As a result of loading such a shift disk, there is produced in the memory _ of supervisory computer 3D a list of entries. Eaσh suσh entry inσludes a name, a phone number, a designation as to primary attendant or auxiliary attendant, and a designa¬ tion as to active or inactive. If an attendant is scheduled to be a primary attendant, 5 but either does not respond when called, or refuses σalls, it is desirable to replaσe that attendant with an auxiliary attendant on an automatiσ basis without requiring interven¬ tion by the supervisor. The operations relating to this automatic feature 0 involve, as indicated in block 29K, determining whether an attendant has refused calls. To provide an indication to the system of the decision to refuse calls, a person can, while on line to the system, use the touch tone keypad on the multi-purpose station to initiate the genera- 5 tion of a predetermined in-band signal. Upon detection of this predetermined signal and σommuniσation of its reσeipt within a status paσket, supervisory computer 3D can proceed to perform appropriate functions without manual intervention by the supervisor. If an attendant did not refuse calls, the flow proσeeds to bloσk 29L. In bloσk 29L, supervisory σomputer 3D determines whether an attendant did not answer. If an attendant did not answer, the flow proσeeds to bloσk 29M in whiσh supervisory σomputer 3D updates the list to mark the attendant's entry to indiσate the attendant is absent. If an attendant refuses calls, the flow proσeeds from bloσk 29K to bloσk 29N, in whiσh supervisory σomputer updates the list to mark the attendant's entry to indiσate the attendant has refused σalls. After either bloσk 29M or bloσk 29N, the flow proσeeds to bloσk 290, in whiσh supervisory computer 3D determines whether any auxiliary attendants are available to replace a candidate attendant. If not, the flow proceeds to block 29P in which supervisory computer 3D updates the list to mark the attendant's entry to indicate the attendant is inaσtive. Otherwise, the flow proσeeds to bloσk 29Q, in whiσh supervisory computer 3D updates the list by replacing the attendant's entry with an available auxiliary attendant's entry. Next, the flow proceeds to bloσk 29R, in whiσh supervisory computer 3D marks the auxiliary attendant's entry to indicate that the attendant is no longer available in the pool. Next, the flow proceeds to block 29S, in which supervisory computer 3D determines whether further processing is needed with respect to status data for other line cards reported in the status packet being proσessed. If so, the flow loops baσk to re-enter bloσk 29K; otherwise, it loops baσk to re-enter - bloσk 29A. With referenσe to the flow σhart of FIG. 30, there will now be desσribed. the operations of a seσond of the independent processes, this process being for real-time timing and automatic functions. In block 30A, supervisory computer 3D determines whether the time or date has changed (i.e. by a sufficient increment, whiσh for real-time clock purposes is one second) . If not, the flow loops baσk to re-enter bloσk 30A. This loop has the σharaσteris- tiσs of a "repeat-until" programming σontrol struσture. Upon exiting this repeat-until loop, the flow proσeeds to bloσk 3OB, in whiσh supervisory computer 3D causes a new time and, if necessary, a new date to be displayed (see FIG. 23, e.g., for the location within the displayed status report where date and time are displayed) . Next, the flow proceeds to bloσk 30C in whiσh supervisory σomputer 3D determines whether a ringthrough is in progress. If not, the flow proσeeds to bloσk 30D where supervisory computer 3D determines whether 15 seσonds or less time " remains before the next projected ringthrough. If not, the flow loops back to re-enter block 30A. Otherwise, the flow proceeds to block 30E, in which supervisory computer 3D determines whether shift data have been downloaded for the ringthrough. If not, the flow proceeds to block 3OF, then to block 30G; otherwise, the flow proceeds to block 30G directly. In block 3OF, shift data are downloaded. That is, data that have been pre-recorded on disk and read into memory of supervisory computer 3D are sent to controlling computer 3C. In bloσk 30G, super¬ visory computer 3D determines whether the time has arrived to start the ringthrough. If so, the flow proceeds to block 3OH then loops back to re-enter block 30A; otherwise, the flow loops back directly. In block 3OH, the ring¬ through is star-ted by placing calls to all attendants in a shift for the ringthrough. If it is determined in block 30C that a ringthrough is in progress, the flow proceeds to bloσk 301 in whiσh supervisory computer 3D determines whether the time has arrived to end the ringthrough. If not, the flow loops baσk to re-enter bloσk 30A. If it has, the flow proσeeds to a bloσk 30J in whiσh supervisory σomputer 3D ends the ringthrough by σooperating with σontrolling σomputer 3C to disσonneσt all the attendants, then proceeds to block 3OK in which supervisory computer 3D finds and sets the next shift and ringthrough time and then loops back to re-enter block 30A. With reference to FIG. 31, there will now be described the operations of a third of the three independent proces¬ ses, this process being for the user interface. In block 31A, supervisory computer 3D determines whether the super¬ visor has issued a request, through either the keyboard or the mouse. As stated above, σonventional mouse driver programming is inσluded within the software for supervisory computer 3D. Through reference to a σombination of vari¬ ables that are σontrolled by suσh mouse driver programming, supervisory computer 3D makes the determination whether a request is pending. If no request is pending, the flow loops back to re-enter block 31A. This loop has the σharaσteristics of a "repeat-until" programming control struσture. Upon exiting this repeat-until loop, the flow proceeds through a series of test blocks that correspond to a programming "case" control structure within a loop such that the flow re-enters block 31A. In the case of a request to change the line card which is being monitored, the flow proceeds from block 31B to block 3IC. The display pointer desσribed above with referenσe to FIG. 23 indiσates to the supervisor whiσh line σard is providing monitor audio to supervisory Station II. A variable keeps track of which one of the line cards is being monitored. When the supervisor wants to change the line σard being monitored from a first line σard to a seσond line σard, the supervisor moves the mouse to position the mouse cursor so that it is placed next to the box for the second- line card, and then cliσks the mouse button. This σonstitutes a request to whiσh supervisory computer 3D responds by updating the above-mentioned variable to identify the second line card, and by repositioning the display pointer, and so forth, to change the line card being monitored. Supervisory σomputer 3D further responds to the request by sending supervisory σommands to σontrolling σomputer 3C to σause it to send digitally σoded σommands to the first and seσond line cards to disable the monitor audio on the first line card and to enable it on the seσond line σard. In the σase of a request to send a supervisory σommand to controlling computer 3C, the flow proceeds from block 3ID to block 3IE. The operations of block 3IE are described below with reference to FIG. 32. In the case of a request for a σonfiguration command, the flow proceeds from block 3IF to block 31G. The operations of blσσk 31G are desσribed below with referenσe to FIG. 33. In a case of a request for a" shift command, the flow proceeds from block 31H to block 311. The operations of block 311 are described below with reference to FIG. 34. With reference to FIGS. 32A and 32B, there will now be described the operations for processing a supervisory command to be sent to controlling computer 3C. These operations begin in block 32A, are entered from bloσk 3ID (FIG. 31) , and exit to bloσk 31A (FIG. 31) . The flow proceeds through a series of test blocks that correspond to a programming "case" control structure. FIG. 32A shows that, in the σase of a command to initialize one or more lines, the flow proceeds from block 32A to bloσk 32B, in which at least one line card is initialized. For each line card that is initialized during block 32B, supervisory computer 3D sends supervisory commands to controlling computer 3C, and it in turn sends digitally coded commands to the line card to be decoded by decoders 21A-21D desσribed above. " These initialization σommands plaσe the line σard in a predetermined state, in whiσh both the σirσuitry for the inσoming line station connection controller and the cirσuitry for the outgoing line ' station σonneσtion σon¬ troller are off hook and busy. Further, status reσords maintained in a status file in σontrolling σomputer 3C are set to σorrespond to this predetermined state. This status file is disσussed below with referenσe to FIG. 35, the flow σhart for the outer loop of operation of σontroll¬ ing computer 3C. ~ In the case of a supervisory command to busy one or more line σards, the flow proσeeds from bloσk 32C to bloσk 32D. As indiσated in the pull-down menu shown in FIG. 24, "Busy WATS" is one of the sub-seleσtions available in the pull-down menu, beneath the "Change" main menu item. Further, beσause the pull-out menu that is presented upon σliσking on "Busy WATS" presents options as to all, random, etσ., one or more line cards can be identified by the supervisor to be placed in a busied-out condition. For each suσh line card, supervisory computer 3D and σontrolling computer 3C cooperate to cause the ground start simulating switσh on the line σard to σlose to busy-out the inσoming line. In the case of a supervisory command to unbusy one or more line cards, the flow proceeds from block 32E to bloσk 32F. As indiσated in the pull-down menu shown in FIG. 24, "Unbusy WATS" is one of the sub-selections avail¬ able. Further, because the pull-out menu that is presented upon σliσking on "Unbusy WATS" presents options as to all, random, etc., one or more line cards can be identified by the supervisor to be placed in an unbusy σondition. For eaσh such line card, supervisory computer 3D and controlling computer 3C cooperate to cause the ground start simulating switch on the line card to open, to unbusy the incoming line. In the case of a supervisory command to disconneσt one or more lines, the flow proceeds from block 32G to block 32H, and, if all lines are to be disσonneσted, through bloσks 321 and 32J. If one or more but not all the lines are to be disσonneσted, the flow proσeeds from bloσk 32H to bloσk 32K. As indiσated in the pull-down menu shown in FIG. 24, "Disσonneσt" is one of the sub- seleσtions available beneath the "Change" main menu item. Further, beσause the pull-out menu that is presented upon clicking on "Disconneσt" .presents options as to all, random, etc., one or more line cards can be identified by the supervisor to be disconnected. For each such line card, supervisory computer 3D and controlling computer 3C cooperate to cause the circuitry for the station connection controller for the outgoing line to disconneσt the atten- dant. If all attendants have been so disσonneσted, in block 32J, supervisory σomputer 3D finds and sets the next shift and ringthrough time. With reference to FIG. 32B, in the case of a super¬ visory command to call one or more lines, the flow proceeds from block 32L to 32M, and if one or more but not all of the lines are to be called, to block 32N. As indicated in the pull-down menu shown in FIG. 24, "Call" is one of the sub-selections available in the pull-down menu beneath the "Change" main menu item. Further, because the pull-out menu that is presented upon cliσking on "Call" presents options as to all, random, etc., one or more line cards can be identified to have a call placed " to an attendant. For each such line card, supervisory computer 3D and controlling computer 3C cooperate to cause the circuitry for the outgoing line station connection controller to go off hook and dial an attendant and retry if necessary until a security verification signal is received. If all • lines are to be called, the flow proceeds from block 32M to block 320, in which supervisory computer 3D determines whether shift data have been downloaded. If not, the flow proσeeds to bloσk 32P, in whiσh supervisory σomputer 3D downloads shift data for this ringthrough. Either after bloσk 32P, or if it is determined in bloσk 320 that shift data have already been downloaded, the flow proσeeds to bloσk 32Q, in whiσh supervisory computer 3D starts the ringthrough by calling all the attendants. With reference to FIGS. 33A and 33B, there will now be described the operations for processing a system con¬ figuration σommand. These operations begin in bloσk 33A, are entered from bloσk 31F (FIG. 31) , and exit to block 31A (FIG. 31) . The flow proceeds through a series of test bloσks that σorrespond to a programming "σase" σontrol struσture. The σonfiguration σommands inσlude σommands affeσting the displayed status report and σommands affeσting global or system level parameters. As indiσated in FIG. 23, the main menu line inσludes items for "Symbols," and for "Numbers," and for "Monitor." These σonfiguration σommands affeσt the displayed status report and are involved in the operations depiσted in FIG. 33A. In the σase of a σonfiguration σommand to toggle the line numbers on the display, the flow proσeeds from bloσk 33A to bloσk 33B, in whiσh supervisory σomputer 3D deter¬ mines whether line numbers are presently visible. If they are, supervisory computer 3D enters block 33C in which it causes the line numbers to be erased from the displayed status report. If the line numbers are not visible, supervisory computer 3D enters block 33D and causes the line numbers to be displayed as part of the displayed status report. In the σase of a σonfiguration command to toggle the symbols display, the flow proceeds from bloσk 33E to bloσk 33F. In bloσk 33F, supervisory σomputer 3D determines whether symbols are σurrently being displayed, and, if they are, enters bloσk 33G in whiσh supervisory computer 3D writes to the screen buffer to redraw the screen using color boxes for the displayed status report. If not, supervisory σomputer 3D enters bloσk 33H and redraws the displayed status report using symbols, instead of σolored boxes. In the σase of a σonfiguration σommand to σhange the monitor line side, flow proσeeds from bloσk 331 to 33 . In bloσk 33 , supervisory σomputer 3D deter¬ mines whether the σaller side or the attendant side is being monitored. If the σaller side is being monitored, the flow proσeeds to bloσk 33K. In bloσk 33K, supervisory σomputer 3D σooperates with σontrolling σomputer 3C to switσh to monitor the attendant side of the line. Other¬ wise, supervisory σomputer 3D enters bloσk 33L, in whiσh supervisory σomputer 3D and controlling computer 3C cooperate to cause the monitor audio to be conneσted to the σaller side of the line. With referenσe to FIG. 33B, the σonfiguration commands involved in the operations depicted in FIG. 33B are those associated with the sub-menu presented upon clicking on "Configure" (FIG. 24) . In the case of a change of ring¬ through length, the flow proceeds from block 33M to block 33N, in whiσh the ringthrough length may be set within limits between one and thirty minutes, as determined by the supervisor's entry of the value using the mouse. In the case of a change configuration command to change the ringthrough time, the flow proceeds from block 330 to bloσk 33P, in whiσh the ringthrough time is set to a time within limits between one and thirty minutes, as determined by the supervisor's entry of the time using the mouse. In the case of a change configuration command to change the emergency number, the flow proceeds from block 33Q to block 33R, in which the telephone number for an emergency operator, keyed in by the supervisor using the keyboard, is sent to controlling computer 3C. In the case of a change configuration command in whiσh the supervisor is setting a new number of retries, the flow proσeeds from bloσk 33S to bloσk 33T, in whiσh the number of retries is set to a number within limits between one and five times, as determined by the supervisor's entry of the number using the mouse. With reference to FIGS. 34A and 34B, there will now be described the operations involved in processing shift and attendant commands that the supervisor enters in response to prompting by the displayed status report shown in FIG. 28. These operations begin in block 34A, are entered from block 31H (FIG. 31) , and exit to block 31A (FIG. 31) . This flow of operations involves a series of tests that correspond to a "case" programming control structure. In the case of a supervisory σommand to load a shift disk, the flow proσeeds from bloσk 34A to bloσk 34B, and if a disk is present in the disk drive, to bloσk 34C. If no disk is present in the disk drive, the flow proσeeds to bloσk 34D, in whiσh supervisory computer 3D causes an ' error message to be displayed and then loops baσk to re-enter bloσk 34B. Aσσordingly, a looping aσtion oσσurs until suσh time as the σorreσt disk is plaσed in the disk drive. Eventually when a shift disk is found present in bloσk 31C so that flow proσeeds to bloσk 34C, super¬ visory σomputer 3D gets a list of shifts on the disk, and in bloσk 34E reads eaσh shift so listed from the disk. In the σase of a supervisory σommand to σhange the σurrent shift (resulting from σliσking on "Shift" on the left side of the display of FIG. 28) , the flow proσeeds from bloσk 34F to bloσk 34G, in whiσh the supervisor seleσts a new shift from available σhoiσes. In the σase of a super¬ visory command to cancel an attendant, flow proceeds from block 34H to block 341, in which the supervisor selects each attendant to canσel. Following bloσk 341, the flow proσeeds to bloσk 34J in whiσh supervisory σomputer 3D determines whether an auxiliary attendant is available to replaσe the attendant being σanσelled. It makes this determination on the basis of referenσe to the list of pooled auxiliary attendants. If so, flow proσeeds to bloσk 3 K in which the attendant is replaced with an auxiliary attendant. Then in block 34L, supervisory σomputer 3D marks its reσords to indiσate the auxiliary attendant is no longer available to be assigned to another line σard. In other words, the auxiliary attendant is deleted from the pool. On the other outσome of the test effeσted in bloσk 34 , the flow proσeeds to bloσk 34M, in whiσh supervisory σomputer 3D marks its reσords for the σanσelled attendant as being inaσtive. With referenσe to FIG. 34B, in the σase of a super¬ visory command to cancel an auxiliary attendant, the flow proceeds from block 34N to blocks 340 and 34P, in which supervisory computer 3D prompts the supervisor to select the auxiliary attendant to canσel, and then marks the reσord for the auxiliary attendant as no longer available to be assigned to a line σard. In the σase of a supervisory command to toggle an attendant as active, the flow proceeds from block 34Q to block 34R and then to block 34S. In block 34R, an attendant is selected, and in block 34S, supervisory computer 3D determines whether this selected attendant is active. If so, supervisory computer 3D marks its record for that attendant as being inactive; if not, supervisory computer 3D marks the record for attendant as being active. These occur -in blocks 34T and 34U, respectively. In the case of a supervisory command to change the phone number for the current shift, the flow proceeds from block 34V to blocks 34W and 34X, in which the supervisor selects the attendant and then enters the telephone number. With reference to FIGS. 35 through 62, there will now be described the internal operations of controlling computer 3C in responding to supervisory commands sent to it from supervisory computer 3D and in cooperating with supervisory computer 3D to control line σonneσtion σontrol system IC. FIG. 35 shows a flow chart for the overall outer loop of operations carried out by controlling computer 3C. In block 35A of this outer flow, controlling computer 3C initializes itself. Following initialization, controll¬ ing computer 3C enters its main outer loop which begins in block 35B, in which controlling computer 3C reads commands from, and writes status data to, supervisory computer 3D via modem. Following block 35B, controlling computer 3C enters block 35C to determine whether an incoming command has arrived. If so, the flow proσeeds to bloσk 35D, in whiσh the σommand from supervisory σomputer 3D is proσessed. The operations involved in bloσk 35D are desσribed below with referenσe to FIG. 36. If no inσoming σommand has arrived, the flow proσeeds from bloσk 35C to block 35E, in which controlling computer 3C scans the line cards for status changes. The operations involved in block 35E are desσribed below with referenσe to FIG. 45. Following block 35E the flow proceeds to block 35F, in which σontrolling computer 3C processes status changes and sends them to supervisory computer 3D. The operations involved in bloσk 35F are desσribed below with referenσe to FIG. 46. The flow proσeeds to loop baσk from bloσk 35F to re-enter bloσk 35B. As to the status of the line σards, σontrolling computer 3C maintains an array of database records, with each database record in the array containing numerous fields of data relating to a respective line card. The following PASCAL-language type declarations apply to such fields and to variables referenced in the application program for controlling computer 3C: State_Type = (N0_CARD, { There is no card present. CALL, { Card in normal call state. TFER_CALL) ; { Card in transfer σall state. Status_Type = (HUNG_UP, { Waiting for 2-seσ delay off. IDLE, { Waiting for σonneσt signal. DIALING, { Waiting for operator response READY, { Waiting for inσoming σall. C_I_P, { Call in progress. NOT_READY, { Waiting for att. aσtivation. CIP_HU, { Attendant hung up on σall progress.} CIP_I, { Attendant disσonneσted on σa in progress. } WAIT_NOOP, { Waiting for operator to drop. TFERRED) { Call is transferred. Req_Type = (NONE> { No emergenσy or help reque pending. } EMER, { Emergenσy request is pending. HELP) ; { Help request is pending. TNum_Type = string [14]; Line_RecType = reσord state : State_Type; { The state of the card. status : Status_Type; { The sub-state of the card. waiting, { For one more scan for status. busy. { Line is hardware or softwa busied. } calling, { Are we calling with this card. sw_busy Boolean; { Are we software-busied on th card. } req Req_Type; { Any help/emer requests pendin tnum TNu Type; { The telephone number. retries, { Number retry attempts on t card. } present, { Card present counting flag. al,a2, { The status A for the line. bl,b2, : Integer; { The status B.for the line. end; Lines Type = arra [1..MAX_LINES] of Line_ReσType; Changer_RecType = record line no. { Line number of change, 0 change. } new_a, { The new status byte A. new__b : Integer; { The new status byte B. end; Var Sσan_Line_Number, The line number we are sσanning Cur Mon Side, Whiσh side of the line we a currently monitoring. } Cur_Mon_Line: Integer; { The line we are currently monito ing. } Dumping : Boolean; { Are we dumping the intern database. } Loσal_Aσσess, { Number(s) to exit local PBX. Loσal_Area_Code, { The local area code. Emer_Tele_Num: Num_Type;{ The emergency transfer number. Noof_Retries: Integer; { Retry attendant how many times Lines : Lines_Type; { The line database. Changer_InBuf: { The buffer from Scanner to Cha ger. } Changer_ReσType; Changer_Buf: Bufl28; { The internal buffer for Changer With respect to the database records, the foregoing declarations define the fields and the possible values for each field. The possible values for the state field are those listed in parentheses in the declaration of "State Type"; that is, the possible values are NO_CARD or CALL or TFER_CALL. The possible values for the status field are those listed within parentheses in the declaration of "Status Type"; that is, HUNG_UP through TFERRED. The possible values for each of the waiting field, the busy field, the calling field, and the sw_busy field are Boolean; that is, either true or false. The possible values for the req field (referred to below as the request field) are those listed within parentheses in the declaration of "Req Iype"; that is, NONE or EMER or HELP. The possible values for the tnum field include any string up to fourteen charaσters long. The possible values for the remaining fields, viz, the retries, present, al, a2, bl, and b2 fields, inσlude any integer. With reference to FIG. 36, there will now be described the operations for proσessing supervisory σommands reσeived from supervisory σomputer 3D. These operations begin in bloσk 36A, are entered from bloσk 35C (FIG. 35) , and exit to block 35E (FIG. 35) . These operations involve a series of tests that correspond to a "case" programming σontrol struσture. In the σase of a supervisory σommand to set or retrieve a phone number, the flow proσeeds from bloσk 36A to bloσk 36B, in whiσh σontrolling σomputer 3C serviσes inσoming telephone number σommands. The operations involved in doing this are desσribed below with referenσe to FIG. 37. In the σase of a line σontrol σommand, the flow proσeeds from bloσk 36C to bloσk 36D, in whiσh σontrolling σomputer 3C services line control commands. The operations involved in doing this are described below with reference to FIG. 38. In the case of a monitor σommand, the flow proσeeds from bloσk 36E to bloσk 36F, in whiσh σontrolling σomputer 3C serviσes monitor control commands. The opera- tions involved, in doing this are described below with referenσe to FIG. 41. In the case of a σonfiguration command, the flow proceeds from bloσk 36G to bloσk 36H, in whiσh controlling computer 3C services the σonfiguration σommand. The operations involved in doing this are des- σribed below with referenσe to FIG. 42. In the σase of a help or emergenσy command, the flow proceeds from block 361 to block 36J, in which controlling computer 3C serviσes the help and emergenσy commands. The operations involved in doing this are described below with referenσe to FIG. 43. With referenσe to FIG. 37, there will nowbe desσribed the operations involved in servicing incoming commands that affect telephone numbers. These operations begin in block 37A, are entered from block 36A (FIG. 36), and exit to block 35E .(FIG» 35) . These operations involve a series of tests that correspond to a "case" programming control structure. In the case of a Get phone number command, the flow proσeeds from bloσk 37A to block 37B ' , in which controlling computer 3C copies the σurrent number for the line card (from the database record for the line ' card) into the internal queue to transmit to supervisory computer 3D. In the case of a Set phone number command, the flow proσeeds from bloσk 37C to bloσk 37D, in whiσh σontrolling σomputer 3C σopies the phone number from the σommand buffer into the database reσord for the line σard. In the σase of a Set a row of phone numbers command, the flow proceeds from block 37E to blocks 37F and 37G. In these blocks, controlling σomputer 3C finds the beginning and ending numbers for a row of line σards and, for eaσh suσh line σard, sets the telephone number in the database reσord for the line σard. With referenσe to FIG. 38, there will now be desσribed the operations for serviσing line σontrol σommands. These operations begin in bloσk 38A. The flow enters bloσk 38A from bloσk 36C (FIG. 36) and exits to bloσk 35E (FIG. 35). In bloσk 38A, σontrolling σomputer 3C finds the. first and last line σard numbers for the σommand. In the σase of a Call attendant σommand, the flow proσeeds from bloσk 38B to bloσk 38C, in whiσh σontrolling σomputer 3C carries out operations desσribed below with referenσe to FIG. 39. In the σase of an attendant Disσonneσt σommand, the flow proσeeds from bloσk 38D to bloσk 38E, in whiσh σontrolling computer 3C carries out operations described below with reference to FIG. 40. In the case of a Busy caller supervisory σommand, the flow proσeeds from bloσk 38F to bloσk 38G, in whiσh σontrolling σomputer 3C issues a HW_BUSY_CALLER command (which corresponds to CTL 12 in FIG. 21) to each line card affected by the supervisory command and marks the database record for eaσh suσh line σard as software busy. In the case of an Unbusy caller supervisory command, the flow proceeds from block 38H to block 381, in which σontrolling σomputer 3C issues the HW_SW_COND_BUSY • σommand (whiσh σorresponds to CTL 11 in FIG. 21) to eaσh line σard affected by the supervisory command and marks the database record for each such affected line σard as software unbusy. In the σase of a σard initialize supervisory σommand, the flow proσeeds from bloσk 38J to bloσk 38K, in whiσh σontrolling σomputer 3C issues the HW_INITIALIZE σommand (whiσh σorresponds to CTL 8 in FIG. 21) to eaσh line σard affeσted by the super¬ visory σommand, and, for eaσh affeσted line σard, sets the fields of the database reσord for the line σard to default values. With referenσe to FIG. 39, there will now be desσribed the operations for serviσing a supervisory σommand to use at least one line σard to σall an attendant. These opera¬ tions begin in bloσk 39A, are entered from bloσk 38B (FIG. 38) , and exit to bloσk 35E (FIG. 35) . In bloσk 39A, σontrolling σomputer 3C issues a HW_BUSY_CALLER σommand to busy the σaller side of the line. Thereafter, the flow proσeeds to bloσk 39B in whiσh σontrolling computer 3C disconnects the current attendant, if any, with an HW_0N_H00K command, (which corresponds to CTL 10 in FIG. 21) . Next, the flow proceeds to bloσk 39C, in whiσh controlling computer 3C determines whether there is a phone number for this line. If so, controlling computer 3C downloads the telephone number in block 39D, then in block 39E issues an HW_OFF_HOOK_DIAL command (which., cor¬ responds to CTL 9 in FIG. 21) to cause the line card to place a call. Next, the flow proceeds to bloσk 39F, in which controlling computer 3C sets the σalling field of the database record for the line card to true. With reference to FIG.40, there will now be described the operations for servicing a supervisory command to use at least one line card to disconnect an attendant. These operations begin in block 40A, are entered from block 38D (FIG. 38) and exit to block 35E (FIG. 35) . In block 40A, controlling computer 3C issues a HW_BUSY_CALLER command to busy the incoming line. Next, in bloσk 40B σontrolling computer 3C issues a HW_ON_HOOK σommand to disσonneσt the σurrent attendant from the outgoing line for the σard. Next, in bloσk 40C σontrolling σomputer 3C sets the σalling field of the database reσord for the line card to false. With reference to FIG. 41, there will now be described the operations for servicing supervisory commands to σontrol monitor audio. These operations begin in bloσk 41A, are entered from bloσk 36E (FIG. 36) and exit to bloσk 35E (FIG. 35) . In bloσk 41A, controlling computer 3C determines whether the supervisory command requires monitoring a different line card. If so, the flow proceeds to block 4IB, in which controlling computer 3C issues a HW_MON_OFF command (which corresponds to CTL 29 in FIG. 21) to disable the monitor on the current line card, and then proσeeds to bloσk 41C. In bloσk 41C, σontrolling σomputer 3C determines whether to monitor the attendant side of the line σard. If the attendant side of the line σard is to be monitored, the flow proσeeds to bloσk 4ID, in which controlling computer 3C issues a HW_MON_OPER σommand (whiσh σorresponds to CTL 20 and CTL 28 in FIG. 21) to σause the line σard to σonneσt the monitor audio to the attendant side of the line σard. Otherwise, the flow proσeeds to bloσk 41E, in whiσh controlling computer 3C issues a HW_MON__CALLER command (which corresponds to CTL 21 and CTL 28 in FIG. 21) to monitor the caller side of the line σard. Next, the flow proceeds to block 4IF, in which controlling computer 3C updates variables to refleσt whiσh line αard is the σurrent line σard for monitoring and whiσh side of the line σard is being monitored. With referenσe to FIGS. 42A and 42B, there will now be desσribed the operations for servicing configuration commands. These operations begin in block 42A, are entered from bloσk 36G (FIG. 36), and exit to bloσk 35E (FIG. 35) . In the σase of a supervisory σommand to set the number of retries, the flow proσeeds from bloσk 42A to bloσk 42B, in whiσh σontrolling σomputer 3C sets the number of retries. In the σase of a Set emergenσy transfer number, the flow proσeeds from bloσk 42C to bloσk 42D, in whiσh σontrolling σomputer 3C sets the emergenσy number for the transfers. In the σase of a σommand to Set loσal area σode, the flow proσeeds from bloσk 42E to bloσk 42F, in whiσh σontrolling σomputer 3C sets the loσal area σode. In the σase of a Set loσal PBX exit σode, the flow proσeeds from bloσk 42G to bloσk 42H, in whiσh σontrolling σomputer 3C sets digits to exit the loσal PBX to aσσess outside lines. With referenσe to FIG. 42B, in the case of a command to Get number of retries, the flow proceeds from block 421 to block 42J, in which controlling computer 3C puts the number of retries in the internal queue for transmis¬ sion to supervisory computer 3D. In the case of a Get emergency telephone number supervisory command, the flow proceeds from block 42K to block 42L, in which controlling computer 3C puts the emergency transfer number in the internal transmission queue. In the case of a Get local area code command, the flow proceeds from block 42M to block 42N, in which controlling computer 3C puts the local area code in the internal transmission queue. In the case of a Get local PBX exit σode, the flow proσeeds from bloσk 420 to bloσk 42P, in whiσh controlling computer 3C puts the local exit code in the internal transmission queue. With reference to FIG.43, there will now be described operations involved in servicing help and emergency com- mands. These operations begin in block 43A, are entered from block 361 (FIG. 36) and exit to block 35E (FIG. 35) . In the case of a Transfer emergenσy supervisory σommand, the flow proceeds from block 43A to block 43B, in which controlling computer 3C transfers a caller to the emergency telephone number by.operations desσribed below with refer- enσe to FIG. 44. In the σase of a Help or emergenσy serviσed supervisory command, the flow proceeds from block 43C to blocks 43D through 43G. In these bloσks, σontrolling σomputer 3C sets the request field of the database reσord for the line σard to no request pending; turns monitor off to reσonneσt the audio; monitors the σurrent side of the σurrent line σard; and unbusies the line σard so that σalls σan now be reσeived. With referenσe to FIG. 44, there will now be desσribed the operations involved in transferring the σaller to the emergenσy telephone number. These operations begin in bloσk 44A, are entered from bloσk 43A (FIG. 43), and exit to bloσk 35E (FIG. 35) . In bloσk 44A, σontrolling σomputer 3C determines whether there is a σaller. (The σaller may have hung up after a request was made to transfer the σaller.) Controlling σomputer 3C makes this determination on the basis of status data returned from the line σard. If the σaller is still on line, the flow proσeeds to bloσk 44B, in whiσh σontrolling computer 3C determines ' whether the current line card is being transferred. If it is not, the flow proceeds to block 44C and then to block 44D. Otherwise, the flow proceeds directly to block 44D. In block 44C, controlling computer 3C disables the monitor on the current line card. In block 44D, controlling σomputer 3C σhanges the monitor to the σaller side of the transferring line σard. Next, the flow proσeeds to block 44E, in which controlling σomputer 3C sends information to supervisory σomputer 3D to report on the new side and line for the seleσted monitor audio. Next, the flow proceeds to block 44F, in which controlling σomputer 3C disσonneσts the audio between a σaller and the attendant. Next, the flow proσeeds to bloσk 44G, in whiσh σontrolling σomputer 3C determines whether an attendant is present on this line. (The attendant may have hung up.) Controlling σomputer 3C makes this determination on the basis of status data returned from the line σard. If the attendant is still on line, the flow proσeeds to bloσk 44H, in whiσh σontrolling σomputer 3C issues a HW_FLASH_DISCONN σommand (whiσh corresponds to CTL 13 in FIG. 21) to discon- neσt the attendant. Next, the flow proσeeds to bloσk 441, in whiσh σontrolling σomputer 3C updates the state/status fields for the database reσord for the line card, to TFER_CALL/WAIT_NOOP. If the attendant has hung up, the flow proceeds from block 44G to block 44 , in which controlling σomputer 3C updates the state/status fields for the database reσord for the line σard, to TFER_CALL/HUNG_UP. With referenσe to FIG. 45, there will now be desσribed the operations for sσanning line σards for status σhanges. These operations begin in bloσk 45A, and, as shown in FIG. 35, are entered from either bloσk 35C or bloσk 35D, and exit to bloσk 35F. In bloσk 45A, σontrolling computer 3C issues a command to forσe the CTL 22 signal true to get status A data for the line σard currently being scanned. Next, in bloσk 45B, controlling computer 3C issues a command to forσe the CTL 4 signal true to get status B data for the same line card. Next, in block 45C, controll¬ ing computer 3C determines whether status A or status B data have changed or if it is waiting to get status data from the line card. As soon as the status A and status B data have been retrieved from the line σard and it is found that a σhange has oσσurred, σontrolling σomputer 3C in bloσk 45D reσords the status σhange for further proσessing. Following block 45D or if no change occurred to status A or status B data, the flow proceeds to block 45E, in which controlling computer advances to the next line card to scan. With reference to FIG. 46, there will now be described the operations for processing status changes in sending them to the supervisory σomputer. These operations begin in bloσk 46A, and, as shown in FIG. 35, are entered from bloσk 35E, and exit normally to bloσk 35B. In the case a status change has ocσurred in data reσeived from the line σard, the flow proσeeds from bloσk 46A to bloσk 46B, in whiσh σontrolling σomputer 3C σarries out operations desσribed below with referenσe to FIG. 47. In the case that dumping of status information to the supervisory σomputer is oσσurring, the flow proσeeds from bloσk 46C to bloσk 46D, in whiσh operations are σarried out to dump the internal line database to supervisory σomputer 3D in aσσord with operations desσribed below with referenσe to FIG. 62. In the σase that anything in the internal status buffer is ready to be transmitted, the flow proσeeds from bloσk 46E to bloσk 46F, in whiσh σontrolling σomputer 3C determines whether one row of line σards has been σompletely sσanned and if the time has σome to transmit information to supervisory computer 3D. If so,, the flow proσeeds to bloσk 46G, in whiσh controlling computer 3C copies the internal status buffer into the transmit queue. With reference to FIGS. 47A and 47B, there will now be described the operations for proσessing σhanges from a sσanned line card. These operations begin in block 47A, and, as shown in FIG. 46, are entered from block 46A and exit to block 46C. In the case that no line card is present in ; a slot, but the internal database kept by controlling computer 3C reflects there having been a card present in such slot before, the flow proceeds from block 47A to block 47B, in which controlling computer 3C updates the database record for the line card by marking the state field as NO_CARD, because the σard is now absent. In ' the case that a line card now is present in the slot where one was not present before, the flow proceeds from block 47C to block 47D, in which controlling computer 3C initializes the card and updates the database record for the line card. In the case that the line card is in a HUNG_UP status and not in a two second on-hook delay, the flow proceeds from block 47E to block 47F, in whiσh σon¬ trolling σomputer 3C performs operations neσessitated by the outgoing line being baσk on hook, whiσh are desσribed below with referenσe to FIG. 48. In the σase that any DTMF status information has been returned, the flowproσeeds from bloσk 47G to bloσk 47H, in whiσh σontrolling σomputer 3C proσesses the DTMF status in aσσord with operations desσribed below with referenσe to FIG. 49. In the σase that the status indiσates that the line has gone busy, the flow proσeeds from bloσk 471 to bloσk 47 , in whiσh σontrolling computer 3C processes the line going busy by reporting this information to. the supervisory computer and assigns a true value to the busy field of the database record for the line card. In the case that the status data reσeived indicate that the line has gone unbusy, the flow proceeds from block 47K to block 47L, in which con¬ trolling computer 3C processes the line card going unbusy by sending the appropriate information to supervisory computer 3D and assigns a false value to the busy field for the database record for this line card. With reference to FIG. 47B, in the case that the status data indicate that the caller has conneσted, the flow proceeds from block 47M to block 47N, in which con- trolling σomputer 3C proσesses the σaller σonneσtion by •changing the status field of the database reσord for the line card to C_I_P (i.e., call in progress). In the case that the status data returned indicate that the caller has hung up, the flow proceeds from block- 470 to block 47P, in which controlling computer 3C processes this by carrying out operations described below with reference to FIG. 56. Next, in block 47Q, controlling computer 3C finds the attendant-present status change by monitoring to detect a σhange in the status return of operator σurrent (oσ) whiσh is indiσated by a σhange in binary value of the STA 1 signal (FIG. 22). Next, in bloσk 47R, σontrolling σomputer 3C finds a σhange in status in the Off-Hook-to- attendant status (oh) by monitoring for a σhange in the binary value of the CTL 55 signal (FIG. 22) . Next, in bloσk 47S, σontrolling σomputer 3C determines whether the waiting field of the database reσord for the line σard is true and if the operator σurrent is not equal to the On- Hook status; and, if so, σontrolling σomputer 3C in bloσk 47C assigns the true value, to the waiting field. If not, the flow proσeeds to bloσk 47U, in whiσh σontrolling σomputer 3C determines whether attendant σurrent is now present. It makes this determination on the basis of the STA 1 signal (FIG. 22) that is returned as part of a status word from the line σard. If attendant σurrent is now present, the flow proσeeds . to bloσk 47V; otherwise, it proσeeds to bloσk 47W. In bloσk 47V, σontrolling σomputer 3C sets the status field of the database reσord for the line σard to DIALING. In bloσk 47W, σontrolling σomputer 3'C determines whether attendant σurrent is now absent. If it is, the flow proσeeds to bloσk 47X; other¬ wise, it proσeeds to bloσk 47Y. In bloσk 47X, σontrolling σomputer 3C performs operations oσσasioned by the atten¬ dant's having hung up, as described below with reference to FIG. 59. In block 47Y, σontrolling σomputer 3C updates the status field of the database reσord for the line σard for use in later σo parison operations, and assigns a false value to the waiting field. With referenσe to FIG. 48, there will now be desσribed the operations σarried out in bloσk 47F (FIG. 47) upon the outgoing line having gone on hook. In the σase that the state field of the database reσord for the line card is TFER_CALL, the flow proceeds from block 48A to blocks- 48B, 48C, and 48D. In block 48B, controlling computer 3C changes the status field for the database record for the line card to IDLE. In block 48C, controlling computer 3C downloads the emergenσy telephone number to the line σard. In bloσk 48D, σontrolling computer 3C issues a HW_FLASH_CONNECT command (whiσh σorresponds to CTL 14 in FIG. 21) to σause the line σard to plaσe a σall to the emergenσy telephone number. In the case that the state field of the database reσord for the line σard is CALL, the flow proσeeds from bloσk 48E to bloσk 48F, in whiσh σontrolling σomputer 3C σhanges the status field of the database reσord of the line. card to IDLE. Next, in block 48G, controlling computer 3C determines whether the line card is present, whether there is a phone number for this line card to dial, and whether this line card is in use (as indicated by the Boolean value of the calling field of the database record for the line card) . If so, the flow proceeds to bloσk 48H, in whiσh σontrolling σomputer 3C σompares the number of retries that have been made against the global parameter appliσable to the number of retries to make. Upon determining to make another retry, σontrolling σomputer 3C in bloσk 481 downloads the telephone number, and in bloσk 48J issues a HW_OFF_HOOK_DIAL σommand to cause the line σard to place the call. If σontrolling computer 3C finds in block 48H that the maximum number of retries have already been made, the flow proceeds to bloσk 48K, in whiσh σσntrolling σomputer 3C sends informa- tion to supervisory σomputer 3D as to the laσk of an attendant, and assigns a false value to the σalling field of the database reσord for the line σard, so as to indiσate it is unused. With reference to FIG. 49, there will now be described the operations carried out in block 47H (FIG. 47) , to process DTMF status. In the case of a DTMF HELP request, the flow proceeds from block 49A to block 49B, in which controlling computer 3C services the DTMF HELP request in accord with operations described below with referenσe to FIG. 50. In the σase of a DTMF CANCEL request, the flow proσeeds from bloσk 49C to bloσk 49D, in whiσh σontrolling σomputer 3C serviσes the DTMF CANCEL request to σanσel either help or emergenσy in aσσord with operations desσribed below with referenσe to FIG. 51. In the σase of a DTMF EMERGENCY request, the flow proσeeds from bloσk 49E to bloσk 49F, in whiσh σontrolling σomputer 3C serviσes the DTMF EMERGENCY request in aσσord with operations described below with reference to FIG. 52. In the case of a DTMF STATUS indicating that an attendant has refused calls, the flow proceeds from block 49G to block 49H, in which controlling computer 3C performs operations described below with referenσe to FIG. 53. In the σase of a DTMF status indiσating that an attendant is ready for a σall, the flow proσeeds from bloσk 491 to bloσk 49J, in whiσh σontrolling σomputer 3C serviσes the DTMF aσtivation for another σall in aσσord with operations desσribed below with referenσe to FIG. 54. In the σase of a DTMF status indiσating an emergenσy response, the flow proσeeds from bloσk 49K to bloσk 49L, in whiσh σontrolling σomputer 3C serviσes the DTMF emergenσy serviσer response in aσσord with operations desσribed below with referenσe to FIG. 55. With reference to FIG. 50, there will now be described the operations carried out in bloσk 49B (FIG. 49) . In the case that the state field of the database record for the line σard is TFER_CALL, the flow proσeeds from bloσk 50A to bloσk 50B, in whiσh σontrolling σomputer 3C issues a DTMF CANCEL in test mode, to reσonneσt the audio. In the σase that the state field for the database reσord for the line card is CALL, the flow proceeds from block 50C to- block 50D, in which controlling computer 3C determines whether an attendant is on-line. If so, the flow proceeds from block 50E, in which controlling computer 3C determines whether any help or emergency request is pending, and whether there is no caller. If so, the flow proceeds from block 50E to block 50F, and then to block 50G; other- wise, the flow proceeds directly to block 50G. In block 50F, controlling computer 3C issues the σommand to software busy .the inσoming line to the line card and assigns a true value to the sw_busy field of the database record for the line card. In bloσk 50G, σontrolling σomputer 3C determines whether the status field for the database reσord for the line σard is DIALING. If it is, the flow proσeeds from bloσk 50G to block 50H, and then to block 501; otherwise, the flow proceeds directly to block 501. In block 5OH, controlling computer 3C issues a DTMF CANCEL command in test mode so as to reσonneσt the audio. In bloσk 501, σontrolling σomputer 3C reports data to super¬ visory σomputer 3D to alert it of the pending help request. With referenσe to FIG. 51, there will now be desσribed the operations σarried out in bloσk 49D (FIG. 49) . In bloσk 51A, σontrolling σomputer 3C determines whether an attendant is on-line. If so, the flow proσeeds to bloσk 51B, in whiσh σontrolling computer 3C determines whether a caller is on-line. If not, the flow proceeds from block 51B to block 51C, and then to block 51D; otherwise, the flow proσeeds direσtly to block 51D. In block 51C, controlling computer 3C issues the command to software unbusy the incoming line for the line card and assigns a false value to the sw_busy field of the database reσord for the line σard. In bloσk 51D, σontrolling σomputer 3C sends data to supervisory σomputer 3D as to the σanσella- tion. With referenσe to FIG. 52, there will now be desσribed the operations carried out in block 49F (FIG. 49) . In block 52A, controlling computer 3C determines whether an attendant is on-line. If so, the flow proceeds to block 52B, in which controlling computer 3C determines whether there is a help request currently pending. If so, the flow proceeds to block 52C, in which controlling computer 3C issues a DTMF CANCEL σommand in test mode so as to reσonneσt the audio. Otherwise, the flow proσeeds to bloσk 52D, in whiσh σontrolling σomputer 3C determines whether a σaller is on-line. If not, the flow proceeds to block 52E, in which controlling computer 3C issues the σommand to software busy the inσoming line for the line σard and assigns a true value to the sw_busy field of the database reσord for the line σard. After bloσk 52C, 52E, and 52D (if a σaller is on-line) , the flow proσeeds to bloσk 52F, in whiσh σontrolling σomputer 3C sends informa- tion to supervisory σomputer 3D as to the emergenσy request. With referenσe to FIG. 53, there will now be desσribed the operations σarried out in bloσk 49H (FIG. 49) . In the σase that the state field of the database reσord for the line σard is TFER_CALL, the flow proσeeds from bloσk 53A to bloαk 53B, and then to bloσks 53C, 53D, and 53E; otherwise, the flow proσeeds to bloσk 53F. In bloσk 53B, σontrolling σomputer 3C issues the σommand to busy the inσoming line for the line σard. In bloσk 53C, σontrolling σomputer 3C σanσels the help/emergenσy request to super- visory σomputer 3D. In bloσk 53D, σontrolling σomputer 3C sends information to supervisory σomputer 3D as to the attendant having refused σalls. In bloσk 53E, σontrolling computer 3C updates the states/status fields of the database record for the line card to CALL/IDLE. In block 53F, controlling computer 3C determines whether the state field of the database reσord for the line σard is CALL. If it is, the flow proσeeds to bloσk 53G, in whiσh σontroll¬ ing computer 3C determines whether an attendant is on¬ line. If so, the flow proceeds to block 53H, in which controlling computer 3C determines whether there is a pending help or emergenσy request, and whether no σaller is on-line. If so, the flow proσeeds to bloσk 531, and then to bloσk 53 ; otherwise, the flow proσeeds direσtly to bloσk 53J. In bloσk 531, σontrolling σomputer 3C issues the σommand to busy the inσoming line for the line σard. In block 53 , σontrolling σomputer 3C sends informa¬ tion to supervisory σomputer 3D as to the attendant having refused σalls. Next, in bloσk 53K, σontrolling σomputer 3C σhanges the status field in the database reσord for the line σard to IDLE. Next, in bloσk 53L, σontrolling σomputer 3C determines whether there is a pending help or emergenσy request. If so, the flow proσeeds to bloσk 53M, in whiσh σontrolling computer 3C sends information to supervisory computer 3D to canσel the help/emergenσy requests. With referenσe to FIG. 54, there will now be desσribed the operations σarried out in bloσk 49 , for reσognizing a DTMF aσtivation for another σall. In bloσk 54A, σontroll¬ ing σomputer 3C determines whether the state is TFER_CALL. If it is, the flow proσeeds to bioσk 54B, in whiσh σon¬ trolling σomputer issues the digitally σoded command to cause the line card to busy out the caller side of the line. Next, in bloσk 54C, σontrolling σomputer 3C σanσels the emergenσy request to the supervisory σomputer. Next, in bloσk 54D, σontrolling σomputer 3C σhanges the state/status in its internal reσords to CALL/HUNG_UP. Next, in bloσk 54E, controlling σomputer 3C determines whether the line card outgoing station conneσtion con¬ troller is off-hook and not in a two seσond delay. If it is, the flow proceeds to block 54F, in which controlling computer 3C issues the command to hang up the attendant with a HW_ON_HOOK command. Following block 54A if the state is not TFER_CALL, the flow proceeds to block 54G, in whiσh controlling computer 3C determines whether the state is CALL. If it is, the flow proceeds to block 54H, in which controlling computer 3C determines whether the status is DIALING. If it is, the flow proceeds to block 541, in which controlling σomputer 3C resets the "try again" variable to initialize it for retry σounts in the future. Next, in bloσk 54 , σontrolling σomputer 3C issues the digitally σoded σommand to unbusy the inσoming line by sending the HW_SW_COND_UNBUSY σommand. Next, in bloσk.54K, σontrolling σomputer- 3C updates the status reσord for the respeσtive line σard by setting the status to READY. If in bloσk 54H σontrolling σomputer 3C deter¬ mines that the status is not DIALING, the flow proσeeds to bloσk 54L, in whiσh σontrolling σomputer 3C determines whether the status is either NOT_READY or C_I_P. If it is in either status, the flow proσeeds to bloσk 54M, in whiσh σontrolling σomputer 3C updates the status reσord to indiσate that this line σard is READY. With referenσe to FIG. 55, there now be desσribed the operations σarried out in bloσk 49L, for serviσing DTMF emergenσy serviσer response. In bloσk 55A, σontrolling σomputer 3C determines whether the states/status is TFER_CALL/DIALING. If it is, the flow proσeeds to bloσk 55B, in whiσh σontrolling σomputer 3C σhanges the status field of the database reσord for the line σard to TFERRED. With referenσe to FIG. 56, there will now be desσribed the operations σarried out in bloσk 47P, after σontrolling σomputer 3C determines that a σaller has hung up. In bloσk 56A, σontrolling σomputer 3C determines whether the state is TFER_CALL. If it is, the flow proσeeds to bloσk 56B, in whiσh σontrolling σomputer 3C performs operations desσribed below with referenσe to FIG. 57. In the case that σontrolling σomputer 3C determines that the state is not TFER_CALL, the flow proσeeds to bloσk 56C, in whiσh controlling computer 3C determines whether the state is CALL. If so, the flow proceeds to block 56D, in which controlling computer 3C performs operations described below with reference to FIG. 58. With reference to FIG. 57, there will now be desσribed the operations σarried out in bloσk 56B, after σontrolling computer 3C determines that the caller has hung up during the course of a transfer operation. In block 57A, controll- ing σomputer 3C issues a HW_BUSY σaller σommand to the line σard to busy out the inσoming line. Next, in bloσk 57B, σontrolling σomputer 3C σanσels the pending emergenσy request in the supervisory σomputer 3D. Next, in bloσk 57C, σontrolling σomputer 3C determines whether the status is WAIT_NOOP or HUNG_UP. If it is, the flow proσeeds to bloσk 57D, in which controlling computer 3C determines whether the two-second on-hook delay is in progress. If it is, the flow proσeeds to,bloσk 57E, in which controlling computer 3C updates its internal reσords for state/status to CALL/HUNG_UP. If the two-seσond on-hook delay is not in progress, following bloσk 57D, the flow proσeeds to bloσk 57F, in whiσh σontrolling σomputer 3C σhanges the state/status fields of the database reσord for the line σard to CALL/IDLE. Next, in bloσk 57G, σontrolling σomputer reσalls the attendant in aσσord with the operations des¬ σribed above with reference to FIG. 48. If during block 57C controlling computer 3C determines that the status is neither WAIT_NOOP nor HUNG_UP, the flow proceeds to block 57H, in whiσh controlling computer 3C determines whether the line card is off-hook to the attendant. If it is, the flow proceeds to block 571, in whiσh σontrolling σomputer 3C σhanges the state/status fields of the database reσord for the line σard to CALL/HUNG_UP. Next, in bloσk 57J, σontrolling computer 3C issues a HW_0N_H00K command to cause disconneσtion of the attendant. If in bloσk 57H controlling computer 3C determines that the line card is not off-hook to the attendant, the flow proceeds to block 57K, in which controlling computer 3C changes the state/status fields of the database record for the line card to CALL/IDLE. Next, in block 57L, controlling computer 3C proceeds to recall the attendant in acσord with the operations desσribed above with referenσe to FIG. 48. With referenσe to FIG. 58, there will now be desσribed the operations σarried out in bloσk 56D, after σontrolling σomputer 3C determines that a σaller has hung up during a normal σall. In bloσk 58A, σontrolling σomputer 3C deter¬ mines.,whether the status is C_I_P. If so, the flow proσeeds to bloσk 58B, in whiσh σontrolling σomputer 3C determines whether a help or emergenσy request has been made. If so, the flow proσeeds to bloσk 58C, in whiσh σontrolling σomputer 3C issues an HW_BUSY_CALLER σommand to busy out the inσoming line on the line σard and then proceeds to bloσk 58D, in whiσh σontrplling σomputer 3C σhanges the status field of the database reσord for this line σard to N0T_READY. If in bloσk 58A σontrolling σomputer 3C deter¬ mines that the status is not C_I_P, the flow proσeeds to bloσk 58E, in whiσh σontrolling computer 3C determines whether an attendant has his station conneσted to the outgoing line for the line σard. If not, the flow proσeeds to bloσk 58F, in whiσh σontrolling σomputer 3C issues an HW_BUSY__CALLER σommand so as to busy out the inσoming line for the line σard. Next, in bloσk 58G, σontrolling σomputer 3C determines whether the attendant has hung up. If so, the flow proσeeds to bloσk 58H, in whiσh σontrolling σomputer 3C σhanges the status field of the database reσord for this line σard to HUNG_UP. Next, in bloσk 581, controlling computer 3C issues an HW_0N_H00K command so as to disconnect the outgoing line. If in block 58G controlling computer 3C determines that the attendant has not hung up, the- flow proσeeds to bloσk 58 , in whiσh σontrolling σomputer 3C σhanges the status field of the database reσord for the line σard to IDLE. Next, in bioσk 58K, σontrolling σomputer 3C proσeeds to reσall an attendant in aσσord with the- operations described above with reference to FIG. 48. With reference to FIG. 59, there will now be described the operations carried out after controlling σomputer 3C determines that an attendant has hung up. In the σase that the state is TFER_CALL, the flow proσeeds from bloσk 59A, to block 59B, in which controlling σomputer 3C performs operations desσribed below with referenσe to FIG. 60. In the σase that the state is CALL, the flow proσeeds from bloσk 59C, to bloσk 59D, in whiσh σontrolling σomputer 3C performs the operations desσribed below with referenσe to FIG. 61. With referenσe to FIGS. 60A and 60B, there will now be desσribed the operations carried out in block 59B, after controlling computer-3C determines that an atten- dant has hung up during a transfer (the state being TFER_CALL) . In the case that the status is WAIT_NOOP, the flow proσeeds from bloσk 60A to block 6OB, in which controlling computer 3C determines whether the two-seσond delay is in progress. If not, the flow proσeeds to bloσk 60C, in whiσh controlling computer 3C changes the status field for the database record for the line card to IDLE. Next, in block 60D, σontrolling computer ' 3C performs the. operations required to call the emergenσy number in aσσord with the flow desσribed above with referenσe to FIG. 48. If σontrolling σomputer 3C determines in bloσk 60B that the two-seσond delay has not elapsed, the flow proσeeds to bloσk 60E, in which controlling computer 3C changes the status field of the database record for the line card to HUNG_UP. In the case that the status is not WAIT_NOOP, but the status is DIALING, the flow proσeeds from bloσk 60F, to bloσk 60G, in whiσh σσntrolling σomputer 3C deter¬ mines whether the outgoing line for this line σard is off-hook. If it is, the flow proσeeds to bloσk 60H, in which controlling computer 3C changes the status field of the database record for the line card to HUNG__UP. Next, in block 601, controlling ' computer 3C issues a HW_FLASH_DIS- CONN command to .disconneσt the attendant. If in bloσk 60G σontrolling σomputer 3C determines that the hook switσh simulating switσh for the outgoing line for the line card is not off-hook, the flow proceeds to block 60J, in whiσh σontrolling σomputer 3C σhanges the status field of the database reσord for the line σard to IDLE. Next, .the flow proσeeds to block 6-OK, in which controlling computer 3C σooperates with the line σard to plaσe a σall to the emergenσy number in aσσord with operations desσribed above with referenσe to FIG. 48. With referenσe to FIG. 60B, in the σase of the status field -being TFERRED, the flow proσeeds from bloσk 60L to bloσk 60M, in whiσh σontrolling σomputer 3C issues a HW_BUSY_CALLER σommand to busy the inσoming line for the line card. Next, in bloσk 60N, controlling computer 3C communiσates with supervisory σomputer 3D to σanσel the emergenσy request. Next, in bloσk 60O, σontrolling σomputer 3C issues a DTMF ACTIVATE σommand in test mode to drop the σaller. Next, the flow proσeeds to bloσk 60P, in whiσh σontrolling σomputer 3C determines whether the hook switσh simulating switσh for the outgoing line is off- hook. If so, the flow proσeeds to bloσk 60Q; otherwise, it proσeeds to bloσk 60R. In bloσk 60Q, σontrolling σomputer 3C updates the database reσord for the line σard so that the state/status fields are marked CALL/HUNG_UP. Next, in bloσk 60S, σontrolling σomputer 3C issues a HW__0N_H00K command to disconneσt the attendant. In bloσk 60R, σontrolling σomputer 3C updates the database reσord for the line σard so that the state/status fields are marked CALL/IDLE. Next, in bloσk 60T, σontrolling σomputer 3C performs the operations required to reσall the attendant in accordance with the flow described above with reference to FIG. 48. With reference to FIGS. 61A and 6IB, there will now be described the operations carried out when an attendant has hung up on a normal call. These operations begin in block 61A, are entered from block 59C (FIG. 59), and exit to block 47(Y) . In the σase of the status for the line σard being DIALING, the flow proσeeds from bloσk 61A to bloσk 6IB, in whiσh σontrolling σomputer 3C updates the database reσord for the line σard so that the status is marked IDLE. Next, in bloσk 61C, σontrolling σomputer 3C performs the operations required to reσall the attendant in aσσordanσe with the flow desσribed above with referenσe to FIG. 48. In the σase of the status for the line σard being either NOT_READY or READY, the flow proσeeds from bloσk 61D ' to bloσk 61E, in whiσh σontrolling σomputer 3C determines whether a help or emergenσy request is pending. If so, the flow proσeeds from bloσk 61F to bloσk 61G; otherwise, it proσeeds direσtly to bloσk 61G. In bloσk 61F, σontrolling σomputer 3C issues a HW_BUSY_CALLER σommand to busy out the inσoming line to the line σard. In bloσk 61G, σontrolling σomputer 3C determines whether the hook switσh simulating switσh for the outgoing line is o f-hook. If so, the flow proσeeds to bloσks 61H and 611; otherwise, it proσeeds to bloσk 61J and 61K. In bloσk 61H, σontrolling computer 3C updates the database record for the line card so that the status field is marked HUNG_UP. In block 611, controlling computer 3C issues a HW__ON_HOOK command to put the outgoing line back on-hook. In block 61J, controlling computer 3C updates the database record for.the line card so that the status field is marked IDLE. In bloσk 61K, σontrolling σomputer 3C performs the operations requiredto reσall the attendant, in aσσord with the flow desσribed above with referenσe to FIG. 48. With reference to FIG. 61B, in the case of the status for the line card being C_I_P, the flow proceeds from block 61L to block 61M, in which controlling computer 3C determines whether a help or emergency request is pending. If either is pending, the flow proceeds to block 6IN, in which controlling computer 3C determines whether -the hook switσh simulating switσh for the outgoing line is off- hook. If it is, the flow proσeeds to bloσk 610; otherwise, it proceeds to block 61P. In block 610, controlling computer 3C updates the database record for the line card so that the status field is marked CIP_HU. In block 6IP, controlling σomputer 3C updates the database reσord for the line σard so that the status field is marked CIP_I. If in bloσk 61M σontrolling σomputer 3C determines that there is neither a help nor emergenσy request pending, the flow 'proσeeds to bloσk 61Q, in whiσh σontrolling σomputer 3C issues a HW_BUSY_CALLER σommand to busy out the inσoming line. Next, in bloσk 61R, σontrolling σomputer 3C issues a DTMF ACTIVATE σommand in test mode to drop the σaller. Next, in bloσk 61S, σontrolling σomputer 3C determines whether the hook switσh simulating switσh for the outgoing line is off-hook. If it is, the flow proσeeds to bloσks 61T and 61U; otherwise, it proσeeds to bloσks 61V and 61W. In bloσk 61T, σontrolling σomputer 3C updates the database reσord for the line σard so that the status field is marked HUNG_UP. Next, in bloσk 61V, σontrolling σomputer 3C issues a HW_0N_H00K command to put the outgoing line back on-hook. In block 61V, controlling computer 3C updates the database record for the line card so that the status field is marked IDLE. Next, in bloσk 61W, σontroll¬ ing computer 3C performs the operations required to reσall the attendant in accord with the flow described above with referenσe to FIG. 48. With referenσe to FIG. 62, there will now be desσribed the operations σarried out to dump the internal database for the line σards from σontrolling σomputer 3C to super¬ visory σomputer 3D. These operations begin in block 62A, are entered from block 46C (FIG. 46) , and exit to block 46Ξ (FIG. 46) . In block 62A, controlling computer 3C determines whether all line σards have been sσanned at least once. If so, the flow proceeds to block 62B, -in which σontrolling σomputer 3C fills the buffer to transmit the status of the line σards, any help or emergenσy re- quests, and the σurrent line σard and the σurrent side of the current line card. Next, in block 62C, controlling computer 3C puts the buffer into the queue to transmit to supervisory computer 3D. The foregoing detailed description disσloses the σonstruσtion and operation of the presently preferred embodiment from a perspeσtive that brings into foσus eaσh of a large number of speσifiσ features, inσluding those provided to take into aσσount many possible events and σirσumstanσes that σan arise at various stages of operation. Beσause of these features, the overall system provides means for sensing many possible events and σirσumstanσes, for reσognizing the oσcurrence or existence of combinations of suσh events and σirσumstanσes, and for determining how to proσeed, either on a fully autonomous basis or under control of supervisory commands entered by the supervisor, so that ensuing operations flow in a branch appropriate for the prevailing circumstanσes. To provide an additional perspeσtive of the presently preferred embodiment, there will now be set forth a summary of operations carried out by the system in its highly advantageous mode of successively extending incoming calls for answer and service by an attendant who remains on line, as during a ringthrough. A. The telephone number for the attendant's multi-purpose station is provided in one of two ways: 1. The supervisor enters the telephone number manually, or 2. The telephone number is loaded into the system from a shift disk. B. The supervisor enters the supervisory command to activate the line card, such that it can be used to respond to inσoming σalls. C. The supervisory σomputer sends the telephone number for the line σard to the σo trolling σomputer. D. The σontrolling σomputer stores the number in the tnum field of the database reσord for the line σard. E. The supervisory σomputer sends to the σontrolling σomputer the supervisory σommand to σall the attendant. F. The σontrolling σomputer sends the σommands to the line σard to software busy the inσoming line and to disσonneσt the attendant, if any (see FIG. 39) . G. The line σard hardware reσords the reσeipt of the σommands and, if there is a σall in progress, defers exeσuting the σommands, and then performs the σommands when there is no longer a σall in progress (see FIGS. 18 and 19) . H. The σontrolling σomputer downloads the telephone number to the line σard and σommands the line σard to go off hook and dial the number (see FIG. 39) . I. The line σard hardware reσords the reσeipt of the off hook and dial command, and if there is a call in progress, defers executing the command until there is no longer a σall in progress (see FIG. 18) . J. Hardware off hook sequenσe (see FIG. 18) : 1. 1/2 seσ - draw dial tone. 2. 1 sec - dwell. 3. 2 sec - DTMF number dial. 4. 30 sec - activation timer. K. Software senses the outgoing line going off hook and dialing and changes the displayed status to "DIALING," (see FIG. 47B) . L. Aσtivation by the attendant or no aσtivation. l. Aσtivation. a. Hardware ends the aσtivation timer and hardware unbusies the inσoming line (see FIGS. 18 and 19) . b. Musiσ is played to the attendant. c. Software senses the aσtivation from the DTMF status returned and software unbusies the inσoming line (see FIG. 54) . d. Software displays the status as "READY" for an inσoming σall. 2. Timer ends with no aσtivation. a. Line σard resets and the σall is ended, 'b. Software senses the outgoing line is baσk on hook and possibly will retry (F, G, H, I, J, K, and L) the aσtivation in multiple mode (see FIGS. 47A and 48) c. Software displays the status as incoming line is "BUSY". M. Hardware senses incoming ring. 1. Two seσond prompt tone. 2. Inσoming and outgoing lines σonneσt through switσh 14C. 3. Software senses the inσoming call and changes the displayed status to "C_I_P" (see FIG. 47B) . N. End of σall - two ways: 1. Caller hangs up. a. The incoming line is hardware busied. b. Software senses the loss of caller and changes the displayed status to "NOT READY" (see FIGS. 47B, 56 and 58). c. The attendant reactivates with a DTMF tone. d. The line σard hardware unbusies the inσoming line upon reaσtivation (see FIGS. 19 and 20). e. Music is played to the attendant. f. Software senses the DTMF status and, based on the DTMF reaσtivation,- changes the displayed status to "READY" (see FIG. 54) . 2. Attendant activation. a. The caller is dropped. b. Unbusy is maintained on the inσoming line. σ. Music is played to the attendant, d. Software senses the loss of the caller and the activation by the attendant and changes the displayed status to "READY" (see FIGS. 47A, 49, and 54) . — M and N repeated upon each incoming call. 0. On hook on the outgoing line - two ways: 1. On hook command issued by software. a. The incoming line is hardware and software busied at the end of the present call. b. Message 2 played (synchronized) . c. Hang up ocσurs at the end of the message. d. Software senses the loss of the attendant and σhanges the displayed status to "IDLE" (see FIGS. 47B, 59, and 61). 2. Attendant hangs up. a. The inσoming line is busied by the hardware. b. The line σard is reset and the outgoing line is hung up. σ. The software senses the loss of the attendant and σhanges the display status to "IDLE" (see FIGS. 47B, 59, and 61). d. The inσoming line is software busied. .e. The software may try to reσonneσt the attendant (see FIG. 48) .

Claims: WE CLAIM: 1. A teleσommuniσations σontrol system for aσσepting a plurality of multi-purpose stations for use as attendant stations in an attendant serviσe σomplex to serviσe σalls directed to the system from originating stations, the system comprising: 'a first plurality of station σonneσtion σon¬ trollers, eaσh station σonneσtion σontroller in the first plurality for σooperating with a respeσtive one of a plurality of multi-purpose stations in defining opposite ends of a σall connection path, and each such station conneσtion σontroller having σontrollable switσhing means for opening the call conneσtion path and releasing the respeσtive multi-purpose station; means for providing seσurity against use of any of the multi-purpose stations within the attendant service complex by an unauthorized person, the means for providing security inσluding means for σontrolling the switching means to open the call conneσtion path and release the multi-purpose station; a second plurality of station connection con¬ trollers, each station σonnection controller in the seσond plurality for σooperating with a respeσtive one of a plurality of originating stations in defining opposite ends of a σall σonnection path; controllable inter-conneσtion means arranged between the first and seσondplurality of station σonneσtion σontrollers; 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 acσording to σlaim 1, wherein the means for providing seσurity inσludes means for receiving a security-σlearanσe signal via the σall σonneσtion path to a multi-purpose station. 3. A system aσσording to σlaim 2, wherein the means for providing seσurity inσludes timer means for defining a timing 'interval to allow for reσeiving the seσurity- σlearanσe signal. 4. A system aσcording 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 logiσ σirσuit means. 5. A system aσσording to σlaim 1, wherein the seσond plurality of station σonneσtion σontrollers are σonneσted to inσoming lines. 6. A system aσσording to σlaim 5, wherein eaσh inσoming line is a ground start line. 7. A system aσσording to σlaim 5, wherein the inσoming lines are connected to the public switched network. 8. A system acσording to σlaim 7, wherein eaσh inσoming line is a ground start line. 9. A system aσσording . to claim 7, wherein each incoming line has a toll-free telephone number. 10. A system acσording to σlaim 9, wherein eaσh inσoming line is a ground start line. 11. A system aσσording to σlaim 1, and further σomprising means for originating σalls from the system to the multi-purpose stations. 12. ' A system aσσording 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 conneσtion controllers are connected to outgoing lines conneσted to the publiσ 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 acσording 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-conneσtion means σomprises a plurality of interσonneσting switσh means, and wherein the means for σontrolling the inter-σonneσtion means σomprises means for σontrolling the interσonneσting switσh means suσh that a plurality of inσoming σalls are extended to the same multi-purpose station during an interval through¬ out whiσh' the multi-purpose station remains σonneσted as an attendant station. _ . 17. A system aσσording to σlaim 16, and further σomprising means for originating σalls from the system to the multi-purpose stations. 18. A system aσσording to σlaim 17, wherein the means for originating σalls from the system σomprises means for generating number-representing signals in a sequenσe to identify a multi-purpose station. 19. A system aσσording to σlaim 18, wherein the first plurality of station σonneσtion σontrollers are σonneσted to outgoing lines connected to the public switched network, whereby the multi-purpose stations can be located in homes. 20. A system acσording to claim 18, wherein the means for originating σalls from the system inσludes means for automatiσally redialing, whereby an interrupted call to a multi-purpose station can be re-established. 21. A system acσording to σlaim 18, wherein the means for originating σalls from the system inσludes means operating automatically in an operation to replaσe an inaσtivated multi-purpose station, whereby an auxiliary attendant σan be substituted to provide serviσe. 22. A system acσording to σlaim 16, and further σomprising in-band signal responsive means for σontrolling the seσond plurality of station σonneσtion σontrollers suσh that an attendant at a multi-purpose station σan disσonneσt an inσoming σall yet remain on line to be ready to have another inσoming σall extended to the on¬ line multi-purpose station. 23. A system acσor.ding to σlaim 1, wherein the system is operable in traffiσ-volume dependent modes, and inσludes means operative during one suσh mode to release a multi-purpose station, then respond to a request to establish a σall connection path for an incoming σall 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-estab¬ lished 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 conneσtion path for an inσoming σall. 25. A system aσσording to σlaim 24, wherein the ringing signal deteσtion 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 σonneσtion controllers are conneσted to outgoing lines σonneσted to the publiσ switched network, whereby the multi-purpose stations σan be loσated in homes. 27. A system aσσording to σlaim 1, and further σomprising means for playing a pre-reσorded message to prompt an authorized person to enter a seσurity-σlearanσe signal. 28. A system aσσording to σlaim 1, wherein the σontrollable inter-σonneσtion means σomprises a plurality of interσonneσting switσh means, and wherein the means for σontrolling the inter-σonneσtion means σomprises means for controlling the interconneσting switσh means suσh that a plurality of inσoming σalls are extended to the same multi-purpose station during an interval through¬ out whiσh the multi-purpose station remains σonneσted as an attendant station, and further σomprising means for playing a pre-reσorded message after the last of the plurality of inσoming σalls and substantially immediately thereafter releasing the multi-purpose station. 29. A teleσom uniσations σontrol system fornetworking a plurality of multi-purpose telephone stations for use as attendant stations in an attendant serviσe σomplex to serviσe σalls direσted to the system from originating stations, the system σomprising: a first plurality of station σonneσtion σon¬ trollers, eaσh station σonneσtion σontroller in the first plurality for σooperating with a respeσtive one of a plurality of multi-purpose stations in defining opposite ends of a σall σonneσtion path; a seσond plurality of station σonneσtion σon¬ trollers, eaσh station σonneσtion σontroller in the seσond plurality for σooperating with a respeσtive one of a plurality of originating stations in defining opposite ends of a σall σonneσtion path; σontrollable inter-σonneσtion means arranged between the first and seσondplurality of station σonneσtion controllers; and means for controlling the inter-conneσtion means suσh that inσoming σalls from originating stations are extended to multi-purpose stations that have been networked for use as attendant stations, and wherein the means for σontrolling the inter-σonneσtion means inσludes means for σausing a plurality of inσoming σalls to be extended to the same multi-purpose station during an interval throughout whiσh the multi-purpose station remains networked as an attendant station. 30. A system aσσording to σlaim 29, wherein the seσond plurality of station σonneσtion σontrollers are connected to incoming lines. 31. A system acσording to σlaim 30, wherein eaσh inσoming line is a ground start line. 32. A system aσσording to σlaim 30, wherein the inσoming lines are σonneσted to the publiσ switσhed 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 inσoming line has a toll-free telephone number. 35. A system aσσording to σlaim 34, wherein eaσh inσoming line is a ground start line. 36. A system aσσording to σlaim 29, and further σomprising means for originating σalls from the system to the multi-purpose stations. 37. ' A system aσσording to σlaim 36, wherein the means for originating σalls from the system σomprises means for generating number-representing signals in a sequenσe to identify a multi-purpose station. 38. A system aσσording to σlaim 37, wherein the first plurality of station σonneσtion σontrollers are σonneσted to outgoing lines σonneσted to the publiσ switσhed network, whereby the multi-purpose stations can be located in homes. 39. A system acσording 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 acσording to σlaim 37, wherein the means for originating σalls from the system inσludes means operating automatically in an operation to replaσe an inaσtivated multi-purpose station, whereby an auxiliary attendant σan be substituted to provide serviσe. 41. A system aσσording to σlaim 29, and further comprising in-band signal responsive means for controlling the second plurality of station conneσtion σontrollers suσh that an attendant at a multi-purpose station σan disσonneσt an inσoming call yet remain off hook to be ready to have another incoming call extended to the off hook multi-purpose station. 42. A system acσording to σlaim 29, wherein the system is operable in traffiσ-volume dependent modes, and inσludes means operative during one suσh mode to release a multi-purpose station, then respond to a request to establish a σall σonneσtion path for an inσoming σall by originating a σall to, and re-establishing the previously released multi-purpose station as an attendant station, and then substantially simultaneously σomplying with the request and extending the incoming call to the re-estab¬ lished attendant station. 43. A system according to claim 42, wherein each of the seσond plurality of station conneσtion σontrollers inσludes a ringing signal deteσtion circuit for detecting such a request to establish a call conneσtion path for an inσoming σall. 44. A system aσσording to σlaim 43, wherein the ringing signal deteσtion σirσuit produσes a signal used to initiate a sequenσe of operations that are σarried out while the ringing signal is present, and that thereby are transparent to the person placing the inσoming σall, by whiσh an outgoing call is completed to a multi-purpose station and thereafter the incoming call is answered. 45. A system aσσording to σlaim 29, wherein the first plurality of station σonneσtion σontrollers are connected to outgoing lines conneσted to the publiσ switσhed network, whereby the multi-purpose stations σan be loσated in homes. 46. A teleσommuniσations σontrol system for seleσtive¬ ly networking a plurality of multi-purpose telephone stations for use as attendant stations in an attendant serviσe σomplex to serviσe calls directed to the system from originating stations, the system comprising: first controllable means σomprising a plurality of outgoing line σonneσtion controllers, each outgoing line conneσtion σontroller for σooperatingwith a respeσtive one of a plurality of multi-purpose stations in defining opposite ends of a call connection path; second σontrollable means σomprising a plurality of inσoming line σonneσtion σontrollers, eaσh inσoming line station σonneσtion σontroller for σooperating with a respeσtive one of a plurality of originating stations in defining opposite ends of a call conneσtion path, and each including means for detecting a ringing signal indicat¬ ing a request to establish a call connection path for an incoming call; third controllable means σomprising a plurality of controllable inter-conneσtion means, eaσh arranged between an incoming line station conneσtion σontroller and an outgoing line station connection controller; fourth controllable means- for originating σalls from the system to the multi-purpose stations via the outgoing line station σonneσtion 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 σompletion of the σall to the multi-purpose station, the inσoming σall is answered and extended to the multi-purpose station by σompleting the inσoming σall at the inσoming line station σonneσtion σontroller and extending the σall to the outgoing line station σonneσtion σontroller via the inter-σonneσtion means. 47. A system aσσording to σlaim 46, wherein the means for originating calls from the system comprises means for generating number-representing signals in a sequenσe to identify a multi-purpose station. 48. A system according to claim 46, wherein the outgoing line station connection controllers are conneσted to the publiσ switσhed network, whereby the multi-purpose stations σan 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 acσording to σlaim 46, wherein the means for originating σalls from the system inσludes 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-σontrolled system σonneσtable between a set of inσoming lines and a set of outgoing lines for using,the outgoing lines to establish a network of multi¬ purpose stations for use by serviσe attendants in serviσ- ing inσoming σalls direσted to the system from originating stations via the inσoming lines, the system σomprising: σontrollable σall extending means for σonneσtion between the inσoming lines and the outgoing lines; σomputer proσess . ing means for σontrolling the σontrollable σall extending means; the σomputer proσessing means inσluding means providing digitally σoded commands to control the call extending means and the call extending means including means providing status data to the σomputer processing means so the call extending means provides for extending incoming calls for answer and service by the serviσe attendants; the call extending means comprising in-band signal deteσtion means operative while a serviσe attendant is serviσing suσh a σall for deteσting the presenσe and source direction of an in-band signal; and the in-band signal detection means communiσating with the means for providing status data to enable the σomputer proσessing means to initiate performanσe of σontrol funσtions in response to the in-band signal. 52. A system aσσording to σlaim 51, wherein the computer processing means responds to predetermined status data to control the call extending means to disconneσt an inσoming σall as a result of an in-band signal reσeived via an outgoing line without disσonnecting a call connection path to the multi-purpose station via the outgoing line. 53. A system acσording 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 acσording 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 acσording to σlaim 51, wherein the inσoming lines are connected to thepublic switσhed network. 56. A system aσσording to claim 55, wherein each incoming line is a ground start line. 57. A system acσording to claim 55, wherein each incoming line has -a toll-free telephone number. 58. A system aσσording to claim 57, wherein eaσh inσoming line is a ground start line. 59. A system aσcording 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-σontrolled 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 σall extending means and the σall extendingmeans inσludingmeans providing status data to the σomputer proσessing means so the σall extending means provides for extending inσoming σalls for answer and serviσe by a group of serviσe attendants in aσσord with an alloσation of tasks determined by the digitally σoded σommands; display means and manual input means for use by a supervisor in interaσtively σontrolling the σomputer proσessing means; the σomputer pro.σessing means being σontinually responsive to status data provided by the σall extending means to generate on the display means a human-readable, σontinually-updated status report by whiσh the supervisor may be prompted to use the manual input means to enter supervisory σommands; and the σomputer proσessing means being responsive to suσh manually entered supervisory σommands to provide digitally-σoded σommands to σause a re-alloσation of tasks. 61. A system aσσording to σlaim 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 inσoming σall is realloσated. 62. A system aσσording. to claim 60, wherein the σomputer proσessing means is responsive to a supervisory σommand to disσontinue extending σalls to a designated serviσe attendant, suσh that the tasks of answering and servicing incoming calls that would otherwise have been alloσated to the designated agent are realloσated. ' 63. A system aσσording to σlaim 60, wherein the σomputer proσessing means inσludes means responsive to status data for aσσumulating statistiσal data base. 64. A system acσording to σlaim 63, wherein the σomputer proσessing means is responsive to a supervisory command to display a selected report of data in the statis¬ tical data base. 65. A system acσording to σlaim 60, and further comprising means for use by the supervisor in selectively partiσipating in a σall. 66. A system aσσording to σlaim 60, and further σomprising means for use by the supervisor in seleσting a call to monitor. 67. A system acσording to σlaim 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 acσording to claim 60, and further comprising means for enabling a serviσe attendant to initiate an operation that automatiσally communicates an audible prompt. 69. A system according to claim 60, wherein the call extending means includes means for σausing a plurality of inσoming σalls to be extended to the same serviσe attendant during an interval throughout whiσh 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 con¬ neσted to the publiσ switσhed network. 71. A system aσσording to claim 70, wherein each incoming line is a ground start line. 72. A system acσording to σlaim 70, wherein eaσh inσoming line has a toll-free number. 73. A system according to claim 72, wherein each inσoming line is a ground start line. 74. ' A system aσσording to claim 60, wherein the call extending means is σonneσted to outgoing lines. 75. A system aσσording to claim 74, wherein the outgoing lines are conneσted to the publiσ switσhed network, whereby a serviσe attendant can service calls at home. 76. A system acσording to claim 60, and further comprising means for originating calls from the system to the service attendant. 77. A system aσσording to σlaim 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 con¬ neσted to the publiσ switσhed network, whereby the multi¬ purpose stations can be located in homes. 79. A system aσσording to claim 77, wherein the means for originating σalls from the system includes means for automatically redialing, whereby an interrupted call to a multi-purpose station can be re-established. 80. A system aσσording to σlaim 77, wherein the means for originating σalls from the system inσludes means, operating automatiσally in an operation to replaσe an inaσtivated multi-purpose station, whereby an auxiliary attendant can be substituted to provide service. 81. A modular line card for use in a telecommuniσa- tions σontrol system for networking a plurality of multi¬ purpose stations for use . -as attendant stations in an attendant serviσe complex to service calls direσted to the system from originating stations, the system being connected to a plurality of lines for incoming σalls 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 conneσ¬ tion 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 σall connection path; a seσond 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 conneσtion path; controllable inter-connection means arranged betweenthe first and second station connectioncontrollers; and means for controlling the inter-conneσtion means suσh 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-conneσtion means inσludes 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.

Inventors: ATKINS CHARLES GARVIS, EFTHYVOULOS NICHOLAS, PROHS JOHN RICHARD, SANDILANDS PHILLIP EDWARD, SCHEID MICHAEL RETUS, ATKINS, CHARLES, GARVIS, EFTHYVOULOS, NICHOLAS, PROHS, JOHN, RICHARD, SANDILANDS, PHILLIP, EDWARD, SCHEID, MICHAEL, RETUS
Applicants: AMBASSADOR COLLEGE
Application year: 1988
Main classification: H04M3
IPC codes: H04M3