Patent GB-1072981-A (GB)
Title: Communications switching systems
Inventor: DUNLAP KERMIT SHOFF
IPC: H04Q3/545
Filed: 1964-07-09
Abstract: 1,072,981. Automatic exchange systems. WESTERN ELECTRIC CO. Inc. July 9, 1964 [July 16, 1963], No. 28285/64. Heading H4K. The ferreed switching networks of an exchange, the trunk circuits for inter-exchange calls, and the junctor circuits for local calls, are arranged in groups termed frames each with their own buffer control circuit which is in. structed in its functions by a central processing complex connected over a common lens to all control circuits. The central processor is provided with data to command the establishment and release of connections, to monitor the supervisory states of various system elements, and to perform various diagnostic operations. Central processor commands, which are mostly in 2-out-of-6 code, are broadcast over the bus and any particular command is accepted by the control circuit for which it is designated by means of signals over a so-called enable and verify cable. This cable comprises wires individual to each control circuit by means of which that circuit is enabled to receive a command and over which the enabled circuit returns a signal to verify its enablement. The command bus is provided in duplicate and commands may be sent over either bus; separate enable and verify cables being provided for each bus. The processor executes a command within 11 Á-secs. whereas the buffer control circuits take about 20 ms. to implement a command. The processor , is therefore in pursuit of several different sequential processes on a time shared asynchronous basis. The central processor is said to include a semipermanent program store and temporary storage facilities and can detect a faulty command and issue a cancellation within 5 m. which is before a control circuit is committed to a response. Other equipment common to the exchange includes a distributer for marking the enable leads to each buffer control circuit and includes a master scanner for the highspeed supervision of specific circuit elements by means of which trouble conditions may be diagnosed. This scanner also acts as a detector for signals in receivers of touch-tone and multifrequency senders for which buffer circuit scanning is too slow. Also provided as common equipment is a teletype unit which prints out information about trouble conditions and can be employed to instruct limited system operations and effect routine changes in central processor temporary stores. A program card writer for the central processor is also included and so is an automatic-message accounting tape unit. The common control complex is not described in any detail. Network arrangement.-Subscriber's lines are connected over a main distribution frame to a number of concentrators termed line switch frames. Each such frame comprises a basic and a supplementary ferreed network unit of two stages interconnected by A-links. Each network unit comprises eight grids each connecting 64 inlets to 16 outlet B-links. The line switch frames are connected over the B-links to line junctor switch frames each comprising upper and lower ferreed matrix networks of two stages interconnected with C-links. Each such network comprises two octal grids. Outlets from the junctor switch frames are connected by way of a grouping frame to one side of junctor circuits arranged in groups termed junctor frames. The other sides of the junctor circuits are accessible to the junctor switch outlets over a two-stage ferreed matrix switching network termed a line junctor link network and comprising upper and lower octal grids. The above network, termed the line link network, is sufficient for talking connections for local calls. Access to inter-exchange trunk circuits and service circuits is had over the grouping frame by way of an array of two-stage trunk junctor switch frames linked to two-stage trunk switch frames. The trunk junctor and trunk switch frames constitute the trunk link network and are of a composition that is similar to that of the line link network. The service circuits are included in the trunk frames and comprise tone circuits, multi-frequency receivers, touchtone receivers, combined dial pulse and touchtone receivers, multi-frequency dial pulse and touch-tone transmitters and recorded announcement circuits. Buffer control circuits.-Subsoribers' terminals in a line switch frame are supervised by a line scanner matrix with its associated buffer control circuit which shares a command and enabling receiver circuit in common with the buffer control circuit of the switching grids of the line switch frame. Each group of line junctor circuits comprising a junctor frame, and each group of trunk and service circuits comprising a trunk frame, are each provided with a scanner and associated buffer control circuit as part of the frame. Each such frame also contains a signal distributer which puts junctors, trunks, or service circuit into and out of commission on commands received from the processor. The line junctor switch frames, the line junctor link network, the trunk junctor switch frames, and the trunk switch frames, employ no scanning of terminals and are served solely by their incorporated buffer control circuits. Each network buffer control unit is divided into two sections each of which normally controls an upper or a lower switching network unit of its frame. If a section of a control circuit encounters trouble or is required for a diagnostic testing routine, it may be placed in a quarantined mode of operation wherein its response to commands is without effect on its network unit. The section of a control unit companion to a section in quarantine mode is placed in a combined mode in which it controls the whole network of the frame and not just its normal network unit. A control unit section may be disconnected by actuation of manual keys to achieve a so-called " power-off " mode of operation. If the companion to a " power-off " section of a control circuit was in a quarantine mode it is automatically put into the combined mode to take control of the whole network. Each control circuit section contains test points for supervision over a diagnostic cable and for diagnosis of trouble conditions over a diagnostic bus for - which purpose the section is directed to a " testpoint-access " mode of operation which mode is compatible with a quarantine mode in the section. The scanner provided in frames with terminal circuits such as involve subscribers' terminals, junctor circuits, and trunk and service circuits, comprises a plurality of ferrods individual to the terminals and by interrogation of which the central processor gains supervision over a scanning bus in accordance with a system programme routine. The buffer circuits provided for each scanner are divided into left and right sections each of which serves half of the scanning leads. Should one section of a buffer circuit be quarantined for fault or testing the other half extends control over the full scanning routine of its frame. The frames of junctor circuits and trunk circuits include buffer control circuits for a signal distributer as well as for a scanner. By means of bipolar signals to each circuit of its frame a signal distributer effects the operation and release of cut-through and by-pass contacts in the circuits. Each distributer comprises a relay translator with a buffer control circuit divided into left and right sections, each section controlling half the circuits of the frame. Each section of a distributer may be put in charge of all the junctor, trunk, or service circuits, of a frame if its companion section is faulty or needed for test. System commands.-The ferreed cross-points are closed and opened under command of the central processor which sets up connections by indicating which terminals, cross-point grids, and links, are required. The connection is established from the aggregate of partial connections set up by each separately instructed section of a buffer control circuit appropriate to the route and as determined by information in the processor. Specific instructions to release cross-points may be necessary but this burden is reduced where ferreed matrices can be differentially wound and such as to release in response to a new path being set up over the matrix. Such a self-clearing matrix is described in Specification 1,051,670. Processor commands are presented in parallel as a 30-bit address, a 6-bit command, a bit to initiate testing termed the false cross and ground or FCG signal, and a bit to effect reset of buffer control circuits when their normal self-resetting procedure is not available. The use of the separate false cross and ground signal to initiate testing allows implementation of a test to be delayed pending establishment of connections for the test. Commands for a line switch frame comprise a " connect" order which marks the ring and tip crosspoint operating coils of the wanted path over the frame and effects the disconnection of the so-called cut-off contacts over which subscriber's terminals are scanned. A " connect-with-cut-off-closed " order may be given to provide scanning facilities for a path which is to be tested from a succeeding line junctor switch frame. A " false-cross-and-ground " order may be given in a testing sequence to open the first stage cross-point contacts of a path in the line switch frame while preserving the line-scanning " cut-off contacts " closed for continued supervision of the line free from interference by the test. A " restore-cut-off " order has a similar effect in releasing all first stage cross-points and restoring line scanning. A " remove-cut-off " order discontinues scanning of an indicated line by opening the cut-off contacts. Commands for a line junctor switch frame, which it is recalled lies between the line switch frames and the junctor circuits, comprise a. " connect " order to establish an indicated path over the frame network and comprise a " connect-with-FCG " order to establish a given path