Patent GB-1100460-A (GB)
Title: Circuit arrangement for indicating a switch position
IPC: H04Q1/24
Filed: 1966-06-29
Abstract: 1,100,460. Automatic exchange systems. TELEFONAKTIEBOLAGET L. M. ERICSSON. 29 June, 1966 [30 June, 1965], No. 29306/66. Heading H4K. In a switching system in which cross-bar (specifically code bar relay) switches are set up by a central processor, each bridge of each switch has an auxiliary set of contacts which indicate the outlet to which the bridge is set, the processor addressing a bridge to obtain as a parallel binary array the auxiliary contact conditions thereby determining if the bridge has been correctly set, or tracing the path of a connection, or restocking switch data records which may have been cleared in the face of fault. The processor D, Fig. 2, selects routes through the switching network A in accordance with the idle/busy conditions listed in its records. To work with the slow acting network components the computer employs interfacial units B and C, C comprising a 16 bit address buffer store BA and a 16 bit result buffer store BR. In the unit B a decoder AO effects addressing and a fast acting register SMR receives instruction data from the processor and controls the network over switch operation units such as VMR and relay operation units such as RMR. Units LT, VT, RT, supply groups of 16 bits to the processor concerning line, switch and relay conditions in the network. The register SMR, Fig. 3, not shown, comprises an array of bistable circuits with 16 circuits in each row. Each row is addressed from the buffer BA and set to register the corresponding bits present in buffer BR. In the set state each bistable operates an associated reed relay. The rows are reset from the buffer BA by means of a second address circuit. The switches described are code relay switches connected for triple group working and in which for each set of ten bridges a set of code bars is selectively displaced to select one out of fourteen vertical arrays of three contact groups each, and at the same time to select one out of the three inlets corresponding to one of the three contact groups. As seen in Fig. 4, an array of twenty such switches KV1-KV20 has bridges VB1-VB10 and associated magnets BM1-BM10. The bridge magnets are pulsed to operate the contacts, release of the magnets leaving the contacts latched mechanically. A switch operating unit VMR, Fig. 4, serves the group of twenty switches and responds to a 16 bit command stored in a row of bistables in the register SMR, by operating code relays S1-S5 to select one of the twenty switches by preparing a circuit for a relay in the group W1-W20, by operating code relays V1-V4 to select a particular one of the ten bridges, and by operating code relays H1-H7 to select those code bars pertinent to the required inlet and outlet of the bridge. The relays S, V and H have checking contacts which provide marks on corresponding ones of a group of sixteen wires terminated on a row of a matrix with capacitative cross-points, Figs. 3 and 5, not shown, the processor addressing the row by way of a transistor matrix to obtain a 16 bit word by means of which it can compare its command with the resulting relay operations. If the command and the result agree, a further row in the register SMR is used to convey a processor command which directly operates the chosen relay W to connect the operating unit VMR to the selected switch. Subsequent commands, relayed by way of the further row in SMR, operate relay K1 to effect code bar displacements and operate relay K2 to operate the chosen bridge magnet. To release the bridge magnet the processor resets the whole of the further row in SMR and promptly rewrites the row less the instruction to operate K2. The interruption in the commands from SMR which cause operation of relays K1 and W is too brief to produce any consequent release. A test is now conducted over the auxiliary bridge contacts Z1 to Z17 to confirm that the bridge has been correctly operated. The bridge common of the auxiliary contacts is split into a set of fourteen corresponding to bridge outlets and a set of three corresponding to inlets, and each portion over decoupling diodes is connected to an individual appearance in a row of a matrix TM each row of which serves all the bridges of one switch. The auxiliary contacts themselves are wired in multiple to a row of the matrix with capacitative cross-points, Figs. 3 and 5, not shown, so that the processor by addressing that row of the matrix can obtain a 16 bit word indicating the state of operation of the switch. As there are seventeen auxiliary contacts two rows of the capacitative matrix have to be employed and the processor must address the matrix twice. To examine the auxiliary contact states the processor places a command in the further row of the register SMR to operate relay K6 in the operating unit VMR, a contact of K6 earthing the required column of the matrix TM as indicated by a contact tree of the relays VIV4. The contact of K6 also earths the required row of the matrix TM as indicated by a contact of the relay W which singles out the required switch. Each crosspoint of the matrix TM comprises resistors R the dividing point of which is connected to one of the bridge commons of an auxiliary contact set. The column wires are connected to 24 volts over resistors R so that earth from the contact of K6 on a column wire and a row wire reduces the potential on the dividing point of the selected crosspoint to earth; all other crosspoints in the matrix being at either 8 volts or 24 volts. The earth appearing on the operated pair of the auxiliary contacts provides the significant inputs to the row of the capacitative crosspoint matrix for reading out to the processor as described above. When the processor has matched the switch condition so indicated with the condition demanded it clears the registrations in the two rows of store SMR to release the relays K, W, S, V and H and free the operating unit VMR for further use.