Patent GB-1344580-A (GB)
Title: Processor controlled communication switching system
IPC: H04Q3/545
Filed: 1972-03-30
Abstract: 1344580 Automatic exchange systems GTE AUTOMATIC ELECTRIC LABORATORIES Inc 30 March 1972 [1 April 1971] 15233/72 Heading H4K  A communication switching system includes a marker sub-system and a register sender subsystem which are interconnected with a dataprocessing unit for processing call data. The marker sub-system is arranged to find idle paths and establish connectors through a switching network independently of the data processing unit and it includes means to detect originating call requests from calling subscriber line circuits and to establish a connection for the call to an idle register junctor. The marker subsystem further includes means effective after the establishment of such a connection to seize a data communication link and transmit an originating data message identifying the calling line circuit and register junctor terminals to the data processing unit. The register sender sub-system includes the register junctors, and means to receive and store call digits for each call; it also includes means for transferring data to the data processing unit. The system utilizes integrated-circuit electronic logic circuits and stored program control. General description.-The common control comprises a register sender sub-system 200, a data processor unit 130 and a maintenance and control center 140. The originating and terminating markers 160, 170 are connected with the central processor 135 of data processor unit 130 via a data link, a communication register 134 and a respective transceiver forming part of the marker system. There is a direct connection between a memory access RMA in the register sender and the central processor. All sub-systems of common control and the markers are duplicated (Fig. 2) so that if any unit is malfunctioning the system can be reconfigured in order to continue call processing. Normally computer A and computer B operate in synchronism and at particular intervals during each clock cycle certain points of the systems are compared and the comparison is monitored by a "third party" circuit, which contains logic enabling it to control the reconfiguration of the system and to perform functions such as controlling one of the computers to analyse the other. The register sender subsystems A and B are likewise operated in synchronism. The originating markers A and B are arranged to process calls simultaneously with the limitation that they cannot both be working with the same network matrix. Each originating marker is capable of taking over the entire work load of the exchange. The terminating markers A and B are arranged so that only one may be serving calls at a time but they are used alternately. Again each terminating marker can handle the entire work load. When traffic warrants it originating marker pairs are provided separately for the line matrix and for the trunk-register matrix in the exchange; the originating marker pair handling incoming trunk traffic can serve up to ten trunk-register groups.  Register sender.-The register sender is generally similar to that disclosed in Specification 1,066,921. It is a time-shared common control unit with the ability to register and process 192 simultaneous calls, and provides the electronic time-shared apparatus for receiving and storing incoming digits and pulse generating sender circuitry to forward a call towards its destination. It includes a plurality of register junctors RRJ which are spacedivided electro-mechanical access circuits for providing an interface between the switching matrices of the system 100 and the time-shared register apparatus, which includes a common logic control 202, a ferrite-core memory RCM to store digits to te received and sent via the register junctors RRJ and supervisory information pertaining to the call under the control of the common logic control 202 via a memory access RMA. A sender-receiver matrix RSX selectively connects a plurality of tone receivers 201 and senders 203 to the junctors RRJ for signalling modes other than the dial pulse mode which is provided for by the junctors RRJ. The senders 203 provide for sending in the multifrequency mode and the receivers provide for receiving in either the touch-calling multifrequency mode from local lines or the multifrequency mode from incoming trunks 152. The time-shared common logic control 202 is duplicated and the two units run identical operations in synchronism with one another. Under normal conditions both units are partially active each serving a respective half of the junctors RRJ. In the case of a unit failing, the remaining unit can serve all the junctors. The control 202, in conjunction with the core memory RCM, performs all functions associated with receiving, sending, and timing of digits. The core memory is a conventional non- destructive read-out memory e.g. a ferrite core memory, and it is used to store information concerning the calls in progress and information relating to the data processor unit 130, i.e. it stores class of service information supplied by the central processor 135, the identity of the junctor in use, the dialled digits received, and control information such as the number of digits to be received before the register sender requests the data processor unit to perform a translation. Data processing unit.-The unit is a general purpose stored program computer with special input-output and maintenance features which enable it to process data. It uses hardware interrupts with eight levels of priority and several sources per level. It has a 2Ás. main memory cycle. It includes a central processor 135; a main ferrite core memory 133 which stores the system executive programs, call processing programs whose frequency of usage requires that they be locally available, and the call history tables of calls in the process of being set up; a drum memory providing for mass storage of translation data, diagnostic programs, tables and other information; and a communication register for interchanging data with the originating and terminating markers. The call processing operation performed by the unit 130 includes the following steps (a) receipt by the unit of a data frame from the originating marker indicating that either a particular local subscriber or a particular trunk has been connected through to a particular junctor BRJ; (b) analysis of the data frame including a register junctor translation which is required to identify the junctor and a class of service translation involving interrogation of the drum memory; (c) storage in the data processor's call history table (addressed by register junctor number) of the data frame and part of the translated class of service information; (d) transfer to the register sender memory of the dentity of the register junctor and part of the class of service information; (e) first and second translations of dialled digit information transferred from the register sender including an intermediate step of informing the register sender of how many digits it should receive before requesting a second translation; (f) in the case of a local termination, the looking up of the local directory number table on the drum memory and the identifying of the line matrix and selector matrix through which the called subscriber can be reached followed by the transmission of a data frame to the terminating marker which enables it to select and pull a path between the called subscriber line circuit and originating junctor to which the calling line is connected; or in the case of an outgoing trunk call, the looking up on the drum memory of the identity of the outgoing trunk group to the connecting office, information for use by the marker in connecting the calling subscriber to one of those trunks, the signalling and sending modes used on the trunk group and alternative routing information, followed by the transfer of the relevant information to the register sender and terminating marker; (g) receipt of a data message from the marker that a path has been completed from the originating junctor to the called subscriber or outgoing trunk; (h) transmission of an instruction to the register sender to cut through the originating junctor and to release the R matrix and register junctor. In addition, maintenance operations are performed including monitoring the system for trouble conditions, trouble access to the system units, routining, storage of information about certain calls being established, trouble diagnosis, and print-out, as well as traffic operations including monitoring equipment usage and overloads, providing the proper response to relieve overload conditions, and providing a means to measure the quality of service. Drum memory.-As indicated the drum memory 131 provides a mass storage medium. It has a control unit which provides control for transferring information between the main core memory 133 and the drum memory 131, on a cycle stealing basis, so that there is no interference with the central processor in accessing the memory 133. For low traffic the drum may be accessed by only one control unit but for high traffic densities the drum is divided into two storage areas and a separate control unit is provided for each. The control unit has the ability to provide two different search modes; the block transfer mode and the associative search mode. The block transfer mode is used in transferring programs and tables between computer core memory and the magnetic drum via the computer memory control (Fig. 2) without interfering with the operation of the central processor. The location of each word on the drum is uniquely defined by the segment number and an angular index value, 1-11,000, which defines a drum location relative to a single fixed reference point (a single pulse on a clock track). A counter advanced one count per drum location is used to develop the index value and the pulses for advancing and resetting this counter are derived from clock tracks written on the drum