Programmable telecommunications switch for personal computer
Contents
1. 370 85 11 FOREIGN PATENT DOCUMENTS 0192894 9 1986 European Pat Off EXTERNAL HOST Lee 111 0 11 05005598409 11 Patent Number 5 598 409 45 Date of Patent Jan 28 1997 0350402 1 1990 European Pat Off 3534918 4 1987 Germany 0358597 3 1990 Germany 4101885 7 1992 Germany 58 69193 4 1983 Japan OTHER PUBLICATIONS Travels Andy Marc and Harry Teleconnect vol 5 Issue 11 pp 39 40 IEEE International Conference On Communications ICC 1990 Paper 211 3 vol 1 15 Apr 1990 Atlanta US pp 128 133 XP147390 Brochure for Model 384 PC Digital Switching Exchange manufactured and sold by Excel Inc Sagamore Beach MA Undated User s Manual for Model 7 384 PC Digital Switching Exchange Undated Primary Examiner Thomas W Brown Assistant Examiner Daniel S Hunter Attorney Agent or Firm Cesari and McKenna 57 ABSTRACT Auser programmable telephone switch which resides within a commercially available personal computer The switch is controllable by either the personal computer s microproces sor or a separate external host connected to an interface provided within the switch The switch includes a CPU matrix card that contains a time slot interchange and a CPU running under a real time operating system The CPU matrix card controls the overall operation of the switch in accor dance wi2. 00 TET fF 5 598 409 Sheet 3 of 4 Jan 28 1997 U S Patent 1 2 5 8 83 00 sng WAL SNE IONLNOD SNLVLS SN NAH Aea eb sbs 509 TONLNOD ONIWIL SANNYL XO 53011 7991 OL THE 3 31 14 sua 34015 33015 3 23 3 3 ear cr 03 0 ONIWIL 910 305535054 9499 eee 92 030 5 598 409 Sheet 4 of 4 Jan 28 1997 U S Patent s t Sis ANNYL SANIT 901 0 OL _ 21 SOTVNV 0 00 ET TET 8 30071 sn 9118 83 8 029 8 9 F S 1297135 910 sna Sha 3 Bas SNE IOYLNOD SNLVLS 21 sna TTTT snag 710344405 5 598 409 1 PROGRAMMABLE TELECOMMUNICATIONS SWITCH FOR PERSONAL COMPUTER This is a continuation of U S Ser No 08 350 589 filed Dec 6 1994 and now abandoned which is a continuation of U S Ser No 08 216 692 filed Mar 23 1994 which is now abandoned which is a continuation of U S Ser No 07 953 690 filed Sep 29 1992 and issued as U S Pat No 5 321 744 on Jun 14 1994 BACKGROUND OF THE INVENTION 1 Field of
3. In brief summary the present invention provides a user programmable telephone switch which resides within a commercially available personal computer The personal computer which typically runs on a widely used applica tion oriented operating system provides a platform for customers that is both easy to program and readily integrat able into existing communication networks The switch is controllable by the personal computer s central processing unit PC CPU a motherboard or plug in PC CPU any of which may act as an internal host Alternatively the switch is controllable by a separate exter nal host connected to interface provided within the switch When an internal host is used all real time call processing is handled by the switch independent of the internal host None of the internal host s resources microprocessor memory disk etc is needed to execute time critical real time tasks Thus all of the internal host s resources are available for use by the application program When an external host is used none of the internal host s resources is needed to control the switch or perform real time call processing tasks The external host s resources are available for use by the application program and the internal host may be used for a completely different application or alternatively held in reserve as a back up should the external host fail Also when an external host is used all that is required to
4. digital line card indicating that a download of instructions is needed downloads instruc tions to said digital line card 25 The system as in claim 17 wherein said message processor of said central call processor downloads instruc tions to said digital line card which include instructions for signalling supervision 26 The system as in claim 17 wherein said message processor of said central call processor downloads instruc tions to said digital line card which include instructions for call inpulsing and outpulsing 27 The system as in claim 17 wherein said message processor of said central call processor downloads instruc tions to said digital line card which include instructions for detection of incoming calls 28 The system as in claim 17 wherein said message processor of said central call processor downloads instruc tions to said digital line card which include instructions for generation of outgoing calls
5. exclusively of said non selected host computer 2 A programmable communications switch system com prising a personal computer including a programmable communications switch including controllable switching means for performing real time call control processing functions including dynamically connecting or disconnecting communi cation paths between various ones of a plurality of ports in re sponse to predetermined messages including means for processing said predetermined messages a time slot interchange and a real time operating system an internal host computer having a first application oriented operating system and being programmable to generate said predetermined messages to control said communications switch an external host computer having a second application oriented operating system and being programmable to generate said predetermined messages to control said communications switch means for interfacing said switching means with said external host computer and host select means coupled to said message processing means for selecting one of said internal or external host computers to control said controllable switching means wherein all real time call control processing is managed by said switching means and wherein when said inter nal host computer is selected to control said commu nications switch said internal host computer runs com munications applications that control said switch exclusively of sa
6. their basic operating power from the PC power bus 9 Although only one digital line card 14 and one analog line card 18 are depicted it should be understood that additional line cards of either type may be added subject to two physical limitations 1 the maximum switching capacity of the CPU matrix card 12 and 2 the physical space within the chassis of the PC 2 An external host 30 which may comprise a separate personal computer workstation or other computer may optionally be connected via a communication channel 32 to the CPU matrix card 12 The CPU matrix card 12 preferably includes a conventional RS 232 compatible interface for connecting the channel 32 The external host 30 preferably operates under an application oriented operating system If desired the switch 10 can reside on a passive backplane no PC CPU 4 or disk 6 present from which its receives electrical power and be controlled by the external host 30 An external battery ring voltage supply 31 is connected via a path 33 to the terminator card 19 Supply 31 may comprise for example a commercially available power supply FIG 2 shows the CPU matrix card 12 in greater detail A central call processor 34 is connected to both the HDLC bus 20 and the LC status control bus 24 The central call processor 34 is also connected with host select circuitry 35 random access and read only memories 36 watchdog timing circuitry 38 input output control circuitry 40 timing an
7. United States Patent 19 Madonna et al 54 75 73 21 22 63 51 52 58 56 PROGRAMMABLE TELECOMMUNICATIONS SWITCH FOR PERSONAL COMPUTER Inventors Robert P Madonna W Barnstable Robert J Buttell Pocasset Mark P Hebert Kingston all of Mass Assignee Excel Inc Hyannis Mass Appl No 651 123 Filed May 21 1996 Related U S Application Data Continuation of Ser No 350 589 Dec 6 1994 abandoned which is a continuation of Ser No 216 692 Mar 23 1994 abandoned which is a continuation of Ser No 953 690 Sep 29 1992 Pat No 5 321 744 H04M 3 00 4 3 22 U S 370 364 379 269 379 284 370 376 Field of Search 379 88 201 268 379 269 279 218 225 284 370 58 3 58 2 References Cited U S PATENT DOCUMENTS 4 009 337 2 1977 Sakai et 379 122 4 228 536 10 1980 Gueldenpfennig et al 370 66 4 527 012 7 1985 Caplan et al 379 284 4 736 406 4 1988 Molnar 379 94 4 736 409 4 1988 Hasegawa et al 379 269 4 908 850 3 1990 Masson et al 379 212 X 4 916 726 4 1990 Morley Jr et al 379 218 X 4 955 054 9 1990 Boyd Jr et al 379 269 4 993 017 2 1991 Bachinger et al 370 58 2 5 007 080 4 1991 MacMillan et al 379 269 5 014 269 5 1991 Picandet
8. d control select circuitry 42 and a time slot interchange TSI 44 Timing and control select circuitry 42 is connected to the TSI 44 the timing control bus 26 for loop timing and to three sources of timing signals which are denoted REF 1 REF 2 which may be supplied by external sources for reference timing and OSCILLATOR which may be sup plied by a free running oscillator located on the CPU matrix card 12 respectively The central call processor 34 which is preferably a Motorola 68302 microprocessor has control over all of the other circuitry on the CPU matrix card 12 The central call processor 34 preferably runs under a real time operating system such pSOS sold by Integrated Systems and preferably uses Q 931 like messages a CCITT standard protocol for communicating over the HDLC bus 20 Using the HDLC bus 20 the central call processor 34 may transmit a message simultaneously to all cards connected to that bus The processor 34 may use the LC status control bus 24 to select a particular card to transmit a message over the HDLC bus 20 The host select circuitry 35 which is preferably a switch operates to inform the processor 34 whether to communicate with the internal hot or the external host upon power up control circuitry 40 which manages all communica tion between the central call processor 34 and the internal host preferably appears as a COMM port or other standard PC I O port on the PC J O bus 8 Timing a
9. he foregoing description has been limited to a specific embodiment of this invention It will be apparent however that variations and modifications may be made to the inven tion with the attainment of some or all of the advantages of the invention Therefore it is the object of the appended claims to cover all such variations and modifications as come within the true spirit and scope of the invention 5 598 409 7 What is claimed and desired to be secured by Letters Patent of the United States is 1 A programmable communications switch system com prising a personal computer including a time slot interchange central call processor configured to perform real time call control processing functions on said time slot interchange and an internal host computer having a first application oriented operating system to run communications applications that control said central call processor and an external host computer having a second application oriented operating system to run communications applications that control said central call processor a host selector coupled to said central call processor configured to select one of said internal and external host computers to control said central call processor wherein said call control processor pertbrms all real time call control processing in response to commands from said selected host computer wherein said selected host computer controls said central call processor
10. her interrogates identified digital line cards 14 using the HDLC bus 20 The processor 34 transmits a message via the HDLC bus 20 and the digital line card 14 responds with a message indicating the line card s status how many ports are provided on the and other information such as whether a download of 40 45 50 55 60 65 basic instructions is needed If download is needed requested by the line card 14 the central call processor 34 will respond by passing the appropriate information previ ously received from the host to the line card processor 46 via the HDLC bus 20 Once all cards present have been identified and interro gated by the central call processor 34 that processor using memory 36 constructs a map or table which includes the PCM address range type of line card and status and type of each port within the switch 10 In addition if a digital line card 14 is identified the central call processor 34 will proceed to delegate appropriate call processing tasks to that line card s processor 46 In a preferred embodiment of the present invention such delegated tasks include signalling supervision call inpulsing and outpulsing instruction con trol and management detection of incoming calls and gen eration of outgoing calls At this point the switch 10 is ready to begin normal operation in accordance with messages received by the CPU matrix card 12 from the host and activity at the ports T
11. id external host computer and wherein when said external host is selected to control said communications switch said external host computer controls runs communications applications that control said communications switch exclusive of said internal host computer 3 The switch system as in claim 2 wherein said internal host computer comprises 8 a personal computer motherboard including an input output bus and a power bus wherein said switching means is connected to both of said busses 4 The switch system as in claim 3 wherein said program mable communications switch further comprises one or more line cards connected in communicating relationship with said switching means for terminating either digital or analog lines or trunks 5 The switch system as in claim 4 wherein each of said one or more line cards for terminating digital lines or trunks comprises 10 second means for processing messages generated by said switching means 6 The switch system as in claim 5 wherein said message processing means of said switching means is operable to distinguish between said one or more line cards and may assign responsibility to said digital line card message pro cessing means for performing one or more predetermined call processing tasks while retaining responsibility for per forming such tasks with respect to said analog line cards 7 The switch system as in claim 2 further comprising means responsive to the message p
12. ine signalling information such as on hook off hook in addition to voice tone signalling in band signalling or data Analog interfaces 62a 62n are preferably separate physi cal modules which may be individually installed on the analog line card 18 Such separate modules may support different signalling protocols thereby advantageously allowing different types of trunks to be terminated on a single analog line card 18 With reference now to FIGS 1 4 the operation of the programmable switch 10 will be described When the switch 10 is initially powered up the PC 2 is turned on basic configuration information and operational system software must be downloaded from a host before initialization pro cedures or any call processing operations may commence The CPU matrix card 12 knows whether to request a down load from the internal host or the external host based on the setting of the host select circuitry 35 After a successful download is completed the selection of either the internal 5 10 15 20 25 30 35 6 host or the external host may be made using messages between the host and switch 10 Following a successful download of configuration infor mation all such information is preferably stored in random access memory 36 on the CPU matrix card 12 The memory 36 is preferably provided with battery backup in order to preserve the configuration information and eliminate the need for re downloading in the f
13. ks pertaining to digital ports that are within the capability of a digital line card s processor Another advantage of the present invention is the high speed of host to switch messaging between the personal computer motherboard and the switch which resides thereon This high messaging speed is achieved by using the standard personal computer bus as the communication chan nel between the internal host and the CPU matrix card BRIEF DESCRIPTION OF THE DRAWINGS This invention is pointed out with particularity in the appended claims The above and further advantages of this invention may be better understood by referring to the following description taken in conjunction with the accom panying drawings in which FIG 1 is a block diagram of a programmable telecom munications switch which resides in a personal computer and which is constructed in accordance with a preferred embodiment of the present invention FIG 2 is a detailed diagram of the CPU matrix card of FIG 1 FIG 3 is a detailed diagram of the digital line card of FIG 1 and FIG 4 is a detailed diagram of the analog line card of FIG 1 DETAILED DESCRIPTION OF AN ILLUSTRATIVE EMBODIMENT FIG 1 shows a commercially available personal computer PC 2 which includes a PC central processing unit CPU 4 and a hard disk drive 6 interconnected by a PC input output I O bus 8 and a PC power bus 9 The PC 2 is preferably a PC AT sold by International Business Machines
14. make the switch operable is a passive backplane for supplying electrical power Physically the switch comprises a plurality of circuit boards or cards which are dimensioned to fit within the chassis of the personal computer A CPU matrix card con tains a time slot interchange and a central call processor microprocessor running under a real time multi tasking operating system The CPU matrix card which includes circuitry for selecting either the internal host or external host to control the switch conducts all communication with the host The CPU matrix card performs or delegates to other intelligent cards within the switch the performance of all real time call processing tasks thus freeing the host from involvement in any real time tasks Four busses provide communication paths between the CPU matrix card and other cards within the switch a timing control bus a line card status control bus a time division multiplex TDM bus for carrying pulse coded modulation PCM voice traffic and analog line signalling and an HDLC or interprocessor bus A fifth bus the battery ring voltage bus is connected only to line cards which terminate analog lines or trunks These five busses are used exclusively by the programmable switch and do not interfere with communications within the internal host such as those between the PC CPU and disk controllers video graphics cards serial or parallel ports or LAN controllers Digital T1 line cards are p
15. muni cations switch said second host computer runs com munications applications that control said communica tions switch exclusive of said first host computer 9 The system as in claim 8 wherein said first host computer further comprises a personal computer motherboard which includes an input output bus and a power bus and said communi cations switch is connected to both of said busses 20 25 30 35 45 50 55 5 598 409 9 10 The system as in claim 9 further comprising one or more line cards connected in communicating relationship with said central call processor said one or more line cards being of a first type for terminating digital lines or trunks or of a second type for termi nating analog lines or trunks 11 The system as in claim 10 wherein each of said one or more line cards for terminating digital lines or trunks comprises means for processing messages generated by said central call processor 12 The system as in claim 11 wherein said central call processor is operable to distinguish between said one or more line cards and may assign responsibility to said digital line card message processing means for performing one or more predetermined real time call processing tasks while retaining responsibility for performing such tasks with respect to said analog line cards 13 The system as in claim 8 wherein said switch further comprises timing selector responsive to said central call process
16. nd control select circuitry 42 as described fur ther below operates in response to instructions from the central call processor 34 to select one of five available signals for synchronizing the CPU matrix card 12 Two such signals are provided by the timing control bus 26 the other three being REF 1 REF 2 and OSCILLATOR 5 598 409 5 TSI 44 which is preferably 512 port non blocking matrix receives incoming PCM voice data via the TDM bus 22 time slots and operates as directed by the central call processor 34 to reorder the time slots and direct them over the bus 22 to the appropriate destinations FIG 3 shows the digital line card 14 of FIG 1 in greater detail The line card 14 includes a line card processor 46 which is connected with the HDLC bus 20 random access and read only memories 48 digital select circuitry 50 HDLC select circuitry 51 elastic stores 52 52 dual framers 54 54 and dual 1 interfaces IF 56a 56n Timing and control circuitry 54 is connected to the timing and control bus 26 identification ID circuitry 49 the digital select circuitry 50 the elastic stores 52a 52n the dual framers 54a 54n and the dual 1 interfaces 56a 56n Line card processor 46 which is preferably a Motorola 68302 microprocessor has control over the other circuitry on line card 14 Processor 46 communicates with the central call processor 34 on the CPU matrix card 12 by exchanging messages over the HDLC bus 20 HDLC
17. or for selecting one of a plurality of synchronization signals available thereto 14 The system as in claim 10 wherein said second host computer is connected with said interfacing means and exclusively controlling said central call processor without said first host computer 15 The system as in claim 8 wherein said messages are generated by said first and second host computers in accor dance with a predetermined format which is independent of the types of line cards that are included in said communi cations switch 16 The system as in claim 10 wherein said analog line cards are connected in communicating relationship with said central call processor by a bus for carrying time division multiplex data a timing control bus and a line card status control bus 17 The system as in claim 10 wherein said switch further comprises a message processor for receiving and processing said predetermined messages and further wherein each of said analog line cards includes means for responding to an interrogation by said message processor by identifying one or more types of signaling protocol modules located on said analog line card 18 The system as in claim 10 wherein said switch further comprises a message processor for receiving and processing said predetermined messages and further wherein each of said analog line cards includes means for responding to an interrogation by said message processor by indicating the 20 25 45 10 n
18. or a compatible thereof Other personal computers having more memory or more powerful CPUs than the PC AT may also be used The PC 2 preferably operates under an application oriented operating system such as DOS or UNIX The PC 2 consists of a chassis or housing in which a motherboard is mounted along with the disk drive 6 and other optional assemblies such as floppy disk drives modems and the like The PC CPU 4 is mounted on the motherboard which includes a series of slots into which other boards cards may be inserted and thereby connected to the PC and power busses 8 and 9 A programmable telecommunication switch 10 resides within the PC 2 A CPU matrix card 12 is inserted into one of the slots on the motherboard and thus connected to the busses 8 and 9 The CPU matrix card 12 is interconnected with a digital 1 line card 14 a digital signal processing DSP card 16 and an analog universal line card 18 and a terminator card 19 by four busses an HDLC or interpro 10 15 20 25 30 35 40 45 50 55 60 65 4 cessor bus 20 a TDM bus 22 a line card LC status control bus 24 and a timing control bus 26 battery ring voltage bus 28 supplies battery voltage 48 VDC and ringing voltage 109 VAC to the analog line card 18 The terminator card 19 serves to physically terminate busses 20 22 24 26 and 28 The line cards 14 and 18 and the DSP card 16 are all connected to and receive
19. period on the order of tens of milliseconds If the host is running under an operating system such as DOS or UNIX which is user or application oriented and not designed for real time operation the real time demands made by the switch will tend to monopolize the host s processing resources This may in turn force the customer to undesirably limit the amount of traffic through the switch so that the host can maintain control This problem is not satisfactorily solved by simply install ing a real time operating system on the host This is because the multitude of real time call processing tasks generated by a switch having a few hundred ports would still occupy so much of the host s resources that the application program could not run properly Moreover most commercially avail able computers which could be used as hosts do not operate on any widely used real time operating system Prospective customers express a strong preference if not an absolute demand for host operating system that is widely used and represents no significant barrier to developing custom appli cations software Another disadvantage of conventional programmable switches is that they can only be connected to one host at a time This means that should the host malfunction or fail the switch will not be controllable and service will be impaired or completely lost 10 15 20 25 30 35 45 50 55 60 65 2 SUMMARY THE INVENTION
20. rocessing means for selecting one of a plurality of synchronization signals available thereto 8 A programmable communications switch system com prising a personal computer including a programmable communications switch including a central call processor configured to perform real time call control processing related to communi cation paths established between various ones of a plurality of ports within said switch said central call processor responsive to predetermined mes sages including a time slot interchange and a real time operating system a first host computer having a first application oriented operating system to an communications applications that control said switch a second host computer having a second application oriented operating system to run communications applications that control said switch means for interfacing said communications switch with the second host computer and host selector coupled to said central call processor con figured to select one of said first and second host computers to control said communications switch wherein all real time call control processing is managed by said central call processor and wherein when said first host computer is selected to contro said commu nications switch said first host computer runs commu nications applications that control said switch exclu sively of said second host computer and wherein when said second host is selected to control said com
21. rovided for terminating digital lines or trunks Each digital line card includes its own microprocessor which under instructions from the CPU matrix card may be used to perform certain real time call processing tasks on board the line card Digital line cards communicate with the CPU matrix card over the HDLC bus Analog line cards are provided for terminating analog lines or trunks Each analog line card may be configured with different modules to terminate lines or trunks having different types of signalling protocols on the same card Other optional cards such as a digital signal processor DSP card may be incorporated into the switch to provide desired services or features 5 598 409 3 In accordance with one aspect of the present invention tasks are architecturally divided according to whether they require real time processing Those tasks which must be performed in real time are the responsibility of the switch as opposed to the internal or external host Further within the switch certain tasks or functions may be delegated by the CPU matrix card to for example digital line cards which contain their own microprocessors having substantial call processing capability This process of delegation is carried out automatically and transparently to the host Consequently the host is relieved of dealing with real time tasks which tend to reduce efficiency and processing speed and the CPU matrix card is relieved of dealing with tas
22. select circuitry 51 under the control of processor 46 is responsible for con trolling the transmission of messages by the line card 14 over the HDLC bus 20 Digital select circuitry 50 is responsible for moving PCM traffic between the TDM bus 22 and the elastic stores 52a 52n On the digital line card 14 the PCM traffic represents only voice tone or data and does not include any line signalling information Each dual T1 interface 56a 56n is capable of terminating two TI spans thus providing a maximum of 96 050 ports out of the total of 512 ports available on the CPU matrix card 12 per digital line card 14 Turning now to FIG 4 analog line card 18 includes timing and control circuitry 58 which is connected to the LC status control bus 24 the timing control bus 26 digital select circuitry 60 and identification ID circuitry 64 which is similar to ID circuitry 49 of FIG 3 Digital select circuitry 60 is connected to analog interfaces 62a 62n LC status control bus 24 and battery ring voltage bus 28 are connected to each analog interface 62a 62n Timing and control circuitry 58 communicates with the central call processor 34 on CPU matrix card 12 via the LC status control bus 24 Digital select circuitry 60 is responsible for moving PCM traffic between the TDM bus 22 and the analog interfaces 62a 62n In contrast with the digital line card 14 the PCM traffic between the analog line card 18 and the TDM bus may also contain l
23. th messages received from the operative host In general those tasks or functions which must be performed in real time are the responsibility of the switch as opposed to the internal or external host Within the switch certain tasks or functions may be delegated by the CPU matrix card to intelligent line cards which contain their own micropro cessors having substantial call processing capability 28 Claims 4 Drawing Sheets 5 598 409 Sheet 1 of 4 Jan 28 1997 U S Patent duv La auva 12 ds 09 7 DIGITAL LINES OR TRUNKS 919 oe 1 lSOH 83 3 J ce sna at 808 2 n erma e ae 8 397210 Nie RDS U e J 5 598 409 Sheet 2 of 4 Jan 28 1997 U S Patent La 2 Old _ 8 ss 0 60 2 109135 108102 ONIWIL 3 1904 4YOSS390Nd 9 30018 NON v9 ISL 330 C 88 1 SNE 10 81 03 7 ONIWIL 18 0 18 83
24. the Invention The present invention relates generally to the field of telecommunications and more specifically to a program mable telecommunication switch which may reside within a personal computer 2 Discussion of the Prior Art User programmable telecommunication switches are used in a wide variety of applications such as voice messaging telemarketing services and the like A programmable switch is usually controlled by a host device which is typically a computer that runs an application program A customer may either purchase a commercially available application pro gram that is compatible with the host and switch hardware or may elect to write a custom program As the application program runs the host issues instruc tions to the switch by way of a communication channel The switch responds to these instructions by taking appropriate action which may include issuing a response to the host to confirm receipt or execution of the instructions Conventional programmable switches exhibit several dis advantages which unduly limit their utility in many appli cations For example a conventional switch that requires its host device to become involved with call processing tasks that must be performed in real time creates a significant processing burden on the host The term real time is used herein to refer generally to call processing e g sending or receiving digits or other tasks which must be executed within a time
25. umber of signaling protocol modules located on said ana log line card 19 The system as in claim 10 wherein said digital line cards are connected in communicating relationship with said central call processor by a bus for carrying messages bidi rectionally a bus for carrying time division multiplex data and a timing control bus 20 The system as in claim 10 wherein a second message processor of each of said digital line cards transmits one or more messages to said message processor of said central call processor which indicates the status of the digital line card 21 The system as in claim 20 wherein said second message processor of each of said digital line cards transmits one or more messages to said message processor of said switch which indicates the types of ports provided by the digital line card 22 The system as in claim 20 wherein said second message processor of each of said digital line cards transmits or more messages to said message processor of said switch which indicates how many ports are provided on the digital line card 23 The system as in claim 20 wherein said second message processor of each of said digital line cards transmits one or more messages to said message processor of said switch which indicates whether a download of instructions is needed by the digital line card 24 The system as in claim 17 wherein said message processor of said central call processor in response to receiving a message from a
26. uture should the switch 10 experience a power loss The configuration information typically includes basic instructions as to how to control each type of port that the switch may have Such instructions are stored in memory 36 on the CPU matrix card 36 for all analog ports but are downloaded and stored in memory 48 on the digital line card 14 for digital ports as described below Such information also preferably includes synchronization priority informa tion which specifies an order in which the five possible synchronization signals available to the timing and control select circuitry 42 should be used to synchronize the CPU matrix card 12 At this point the central call processor 34 proceeds to interrogate all other cards present within the switch 10 The processor 34 uses the LC status control bus 24 to interrogate all line cards both digital and analog and to receive responses from their respective ID circuitry These responses indicate to the processor 34 what types and the number of line cards present Subsequently the central call processor 34 will further interrogate the identified analog line cards 18 again using the LC status control bus 24 In responding to this further interrogation the analog interfaces 62a 62n identify the types of modules signalling protocols they represent the number of modules etc This information is retained in the memory 36 on the CPU matrix card 12 Similarly the central call processor 34 furt
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