Patent GB-818876-A (GB)
Title: Improvements in or relating to electric signalling systems
IPC: H04Q3/00
Filed: 1956-11-27
Abstract: 818,876. Automatic exchange systems. STANDARD TELEPHONES & CABLES Ltd. (Standard Elektrizitats Gesellschaft A.G.). Nov. 27, 1956, No. 36237/56. Class 40 (4). A plurality of signals each accompanied by a sequence indicator are transmitted by one apparatus and received by another apparatus which discriminates between the sequence indicators and controls reception of the signals in correct order. Transmission of digits. Figs. 1 and 1A show a circuit for the reception of dialled digits and subsequent transmission as combinations of frequencies to a distant exchange. When the circuit is taken into use relays C and P operate to energize the first winding of H1 which locks up over its winding II in series with H2 (I). Dialled impulses are repeated by A to switch magnet Za1. Relays U3, U4 hold up during each train of impulses and then fall back slowly. When U3 has fallen back but before U4 has restored, relay HI releases. When U4 has restored H3, (I) locks up in series with H2 (II). The next train is thus sent to switch magnet Za2 and subsequent digits to Za3-Za5. At the end of the fifth train H5 and H6 restore to re-energize H1 which operates U2 so that the succeeding digits are directed to switch magnets Za6-Za10. After the first five digits have been registered sending begins. Operation of U2 energizes V1-V6 in sequence after which they restore in sequence with suitable time delays. As long as V2 is energized a frequency combination is sent by the appropriate source ZF1-ZF10 over the appropriate contact and wiper of switch Za1 to hybrid transformer GU. Simultaneously, a single frequency F1 is directed to the other input of GU which sends the combined frequencies to line S1, S2. For the second to fifth digits the single frequency is generated by F2-F5. The first five digits represent an exchange code in a long-distance selection system. When the selector at the tool centre has operated a signal is returned to energize R which sets up R<SP>1</SP>. Relay R falls back at the end of the signal to energize R2 so that the frequency combinations set up on switches Za6-Za10 are now transmitted the digit position being again indicated by frequencies F1-F5. The toll centre again returns a signal to set up R so that R3 energizes to restore C and P. While P is falling back the switches Za1-Za10return to home position. A combination of two frequencies comprises a seizure signal which operates a v.f. receiver E, Fig. 2, to actuate relays A and B, so setting up C1 and C2. C2 grounds wire c1. At the end of a call a release signal similar to the seizure signal restores C1 followed by C2. Group selector and marker, Figs. 3, 4, 4A. The group selector, Fig. 3, is seized over the c wire and the marking relay M1, Fig. 4, corresponding to the selected group selector pulls up. Coupling magnet ko1 locks up to the starting line and prepares an alternative coupling magnet ko2 for the next seizure. Incoming signals are directed to receiver SE 1 to operate one of the tens relays Z1-Z10, Fig. 4A, which connects the c-wires of the appropriate decade to the test relays. One of the free test relays P1-P10 operates to mark the free individual line within the selected decade, so energizing the corresponding units relay E1-E10. The selected units relay energizes coupling magnet ko, Fig. 3, which locks up to the c-wire and releases the marker, the setting selected by the tens and units relays connecting the incoming leads a, b, c, to the selected outgoing leads a1, b1, c1. Signal receiver, Fig. 5. The frequency combinations received over wires a, b are amplified and fed to six tuned receiving circuits of which five respond to the frequencies representing digits 1-0. The sixth circuit adjusts itself consecutively to respond to frequencies F1-F5, directing these to gas discharge tube R to actuate relay K. Relay K switches in the receiving circuits for the digit valve to operate two of relays I-V which lock up and energize D and a relay 1-0 corresponding to the digit value. Modified signal receiver, Fig. 6. Six tuned circuits F0-F5 respond to frequencies f0-f5. The first digit is represented by f0 and its value by two of the frequencies f1-f5. The second digit is represented by f and its value by two of f0, f2-f5, the third digit by f2 and its value by two of f0, f1, f3-f5, and so on. Relay KL operates when the receiver is seized. Reception of frequency f0 in the first signal operates transistor TrO and relay K. K restores KL so that relays I-V are connected to receiving circuits F1-F5 via transistor circuits. Relay V1 also pulls up to energize V2 slowly. The evaluation of the digit is effected over contacts 1-5. The operated relays fall back at the end of the signal but before V2 restores it advances switch St to switch the receiving circuits so that the digit position identification relay K is connected to receiving circuit F1 and evaluation relay I is connected to circuit FO. Similar switching takes place at the reception of subsequent digits.