Patent GB-569487-A (GB)
Title: Improvements in electrical signalling systems
IPC: H04H20/81
Filed: 1943-11-20
Abstract: 569,487. Electric control systems. AUTOMATIC TELEPHONE & ELECTRIC CO., Ltd., TAYLOR, R., and BAKER, G. T. Nov. 20, 1943, No. 19426. [Class 40 (i)] [Also in Group XXXIX] In a system for the distribution of programme matter, the inputs and outputs of the amplifiers at the control station A, substations C, G, H, &c. and tandem stations D, E, F can be supervised by an attendant at the control point, there being only one pilot line for supervision between each station and any station to which it is connected. Selection of tandem stations and stations reached indirectly and of amplifiers is effected by means of synchronously operated step by step switches. Means are provided for telephonic communications between the central station and any substation or tandem station. Station selection. When a station-selecting key such as KS, Fig. 3, is operated, the associated relay SK pulls up and locks, energizing SW, which is common to all the stations reached over a particular pilot wire. If the key is that of a directly reached outstation, SW is individual to that station and the wire to the back contact of ic3 is connected to wire SZ. Consequently, SW in addition to extending the pilot wire to relay I and energizing SSW, energizes SZ, all these relays being on a common circuit, Figs. 4 and 5, and the lamp SEL associated with the key glows and indicates the seizure of the station. If the key is that of a tandem station (or a substation reached via a tandem station) back contact ic3 is connected to wire SS instead of wire SZ and SS pulls up followed by SPU. At the tandem station, Figs. 8 and 9, a relay TSA polarized by a rectifier pulls up in series with the relay I, Fig. 4, and energizes a galvanometer relay TRR, e.g. of the kind described in Specification 518,877. This is followed by TPU, TH and the stepping magnet TS of a reverse drive switch. TPU interrupts the line circuit, releasing TSA, and completes a reversing circuit for TRR which releases TPU to allow the switch to step. TRR then swings back to its make position re-operating TPU which drives it back and so on. This interaction continues until TS again reaches its normal position. Each interruption of the line circuit by TPU, releases I at the central station to complete the circuit of the driving magnet CSM, the circuit being interrupted shortly afterwards by the release of SPO which re-operates when I comes up again. The two switches thus move together with CS slightly ahead. Ground connections to one or more of the terminals CS3 over contacts of the station key relay cause operations of the reversing relay RV in those positions and a corresponding operation of TSB in place of TSA at the tandem office. In those positions in which TSA is operated, one or more of relays SA, SB, SC pull up and lock and when the home position is reached again, a circuit is made over contacts of these relays for a relay such as HA which switches the pilot line through to a programme selecting circuit which may be local or may be at a substation. IB pulls up over the line to the programmeselecting circuit and energizes IR. If the central station amplifiers are to be supervised, the relay MSK is operated and this connects the supervisory circuit over wires 21, 22 to a circuit, not shown, to which the inputs and outputs of the various amplifiers can be connected by the operation of the appropriate programme-selecting keys. Programme selection. This is effected by operating a key such as KP1 to energize the associated relay PK which locks up and energizes relay PW to prevent the energization of any other PK relay. If the central station amplifier is to be supervised, MSK is operated and a circuit is made over wire 36 for a relay which connects the required amplifier to wires 21, 22. PZ also is operated and the lamp of the selected programme glows. Normally the output of the amplifier is connected up but if key KI is operated, a relay operated over wire 41 causes the connection of the input instead. If the amplifier is at another station, the programme selecting relay PK energizes PS which energizes RV to reverse the current in the pilot line and so operate PSA in the programme selecting circuit, Figs. 6 and 7, of the selected station. If the circuit is reached via a tandem circuit, Figs. 8 and 9, this action is brought about by the reversal of the connection of IB due to the energization of TSB thereat. PSA energizes RR which is a galvanometer relay similar to TRR described above and RR, PU, energize H and co-operate in the same way as TRR, TPU with I, SPU to cause synchronous rotation of switches PS, CS. If the control is via a tandem office, IB repeats the interruption of the pilot circuit. Certain terminals in bank CS2 are grounded by the programme-selecting relay and the relay IP for selecting the input instead of the output side and in these positions RV reverses the line current to operate PSA (directly or with the help of TSB in tandem connections). This causes the operation of a combination of relays DA ... DC with or without the input-selecting relay IT. Relays DA ... DC select the appropriate switching relay such as TA. At the central station, SZ pulls up when the switch reaches its home position, lights the programme lamp and reverses the line current to re-operate PSA and cause the operation of the selected switching relay. Telephonic communication. If the central station attendant throws key KT, TK pulls up connecting a telephone set in place of the supervisory set 37 to the pilot line over which a programme circuit has been selected as previously described. Switches CS, PS rotate in synchronism as before but no circuit is made for operating RV until the switches reach home again and PZ pulls up. PSA then energizes CT which connects up a telephone set in place of the line to the programme amplifiers and rings bell 57. When tho substation attendant replies A, AR pull up and the bell is cut off. Calls by a substation attendant are made by removing the receiver whereupon A energizes OG which locks and energizes CT to connect up the telephone set. OG also connects battery and ground to the pilot line to operate IC at the central station (with the aid of TIC, TOG at the tandem office if any) and this lights a calling lamp individual to the pilot line and rings a bell. The central station attendant then throws a key of the calling pilot line to operate SK, SW. ICR also is energized and operates SZ which lights the selection lamp corresponding to the key. The telephone key KT is then thrown to operate KT, PZ and complete the connection.