Patent GB-1159251-A (GB)
Title: Improvements in or relating to Signalling Systems
Inventor: RIGBY DONALD FRANK
IPC: H04Q3/42
Filed: 1965-07-29
Abstract: 1,159,251. Automatic exchange systems. H.M. POSTMASTER GENERAL. 29 July, 1966 [29 July, 1965; 24 March, 1966], Nos. 32557/65 and 13101/66. Heading H4K. In a switching system control signals from a control register 15, Fig. 1 to a stage register 102 are sent as a unique combination of a number of discrete current or voltage valves applied one to each conductor of the transmission path. A receiver in the stage register signals to the transmitter when it is ready to receive a combination compares the incoming current or voltage valves with reference valves in order to identify the received values, and signals to the transmitter when a combination has been identified. D.C. voltage sender and receiver is shown in Figs. 2, 3, 4, and 5, in which the control register seizes the D.C. sender by operation of relay SA, Fig. 2, and transmits the first digit stored in the register as energization of one line out of each of the groups of four lines L25-28 and L211 to 214. Contact SA1 puts an earth on signal wire L23, which connects to L33 on Fig. 3, and operates relay BB which via BB1 puts 12V+ve signal on lines L31 and 32 which signal, via rectifiers MN35 and 36 and transistors VT32 and 33, operates relay CP to put the receiver in signal receiving condition, and is reverted to the transmitter as a "proceed to send" signal. The 12V signal received on lines L21-22 Fig. 2, turns on transistors VT21 and 22 which, via transistors VT23 and 24 operate relay SC, which holds over contacts SC4, and applies D.C. voltage signals to lines L21 and 22 over contacts SC1 and 2, the actual voltages applied to the lines depending on which of the relays A to D and W to Z are operated to switch through potentials from the Zener diode chains RZ22 to RZ211. The resulting D.C. potentials received on lines L31 and 32 are applied over operated contacts CP2 and CP3 to lines L41 Fig. 4, and L51 Fig. 5, for evaluation. In Fig. 4, the voltage received from the transmitter line L21 and applied via lines L31 L311 and L41 is compared with reference potentials of earth, V5, V6, and V7 in transistors VT41-VT44 and causes all the transistors to conduct whose reference potential, applied to the emitter, is less than the signal potential. The diode matrix MR411  to 420 is arranged to enable only that transistor of transistors VT45 to VT48 which is associated with the highest numbered operated one of the transistors VT41 to VT44, to cause operation and self hold of one of the relays AA to DA. In a similar fashion the voltage on line L22 is applied over lines L32, L321 and L51 Fig. 5, to cause operation of one of the relays WA to ZA. Contacts of the relays AA to DA and WA to ZA are arranged in a tree as shown on Fig. 3 to provide a selection signal for the common control circuits as a potential on one of the sixteen lines 1 to 16. A signal potential on one of lines 1 to 16 is fed, via one of the diodes MR311 to 326 to turn on transistor VT34 and operate relay SR. Contact SR1 earths line L32 and via line 22, Fig. 2, contacts SC2 and rectifier MR25 turns on transistors VT25 to 27 to operate relay SD. Contacts SD1 puts earth potential on line L29 to signal to the control register that the information has been sent, and received by the stage register, while contacts SD2 open to release the operated ones of relays A to D and W to Z to remove the signalling potential from the lines L21 and 22. SD1 over its back contact removes the hold signal from transistor VT24 and releases relay SC which causes SD to release. Finally VT49, Fig. 4 is turned on to operate relay RL to inhibit the detector circuits and prevent their operation on subsequent switching surges, SR releases when the output goes from the leads 1 to 16, and relay A is released by the control register to restore the equipment to its original condition. In a modification in which each transmitted signal comprises two successive digits sequencing circuits are provided at the transmitter and at the receiver, and a pair of temporary relay stores are provided to store the output from the detector circuits until both digits have been transmitted and the outputs from the stores operate the common control via a translation field. Current signalling sender and receiver shown in Figs. 7 to 12, operates in a similar manner to that described above with respect to Figs. 2 to 5 except that the information signals applied to the lines L71 and L72 are discrete values of current obtained by the switching, by means of relays A to D and W to Z controlled by the control register, of one of the resistors R81 to R84 into the emitter circuit of transistor VT81 and one of the resistors R85 to R88 into the emitter circuit of transistor VT82. At the receiver, after the initial setting up period which is identical with that described above, the coded current signals are fed from line L71, via L91 and contact CP2, to L105, Fig. 10 and from line L72, via line L92 and contact CP3 to L119, Fig. 11. In each current detector, Fig. 10 or Fig. 11, relays e.g. P, Q, R, and S, Fig. 10, are operated one after the other until the current fed to the detector circuit on L105 equals that fed via VT105 and controlled by the relay contacts P3 to S3. At the balance condition the number of relays P to S which are operated will depend on the incoming current and the interconnections of relay contacts P4 to S4 and rectifiers MR109 &c. will cause one only of transistors VT106 to 109 to conduct and mark one of the lines L101 to L104. The current in line 119 will similarly cause one of lines 115 to 118 to be marked and the combination marking in the relay matrix of Fig. 12, will cause one of the relays 1R to 16R to operate and mark one of the lines L1 to L16 leading to the common control. The release of the apparatus then proceeds in a similar fashion to that described with respect to Fig. 2 to 5. An alternative embodiment is described for the transmission and reception of successive pairs of information signals similar to that referred to above after the description of Figs. 2 to 5.