Patent GB-638213-A (GB)
Title: Improvements in or relating to manual telephone exchange systems
IPC: H04M3/60
Filed: 1947-09-10
Abstract: 638,213. Exchange systems. STANDARD TELEPHONES & CABLES, Ltd. Sept. 10, 1947, No. 24850. Convention date, Oct. 23, 1945. [Class 40 (iv)]  In a system having a number of manual positions for dealing with toll calls and having means for distributing calls over the positions that are staffed at any time, means are provided by which a call relating to a previous request or call may be transferred to the posi-  tion that handled the previous request or call or alternatively to another position which has taken over the traffic of that position. For this purpose, each position has a switch OS which may be set either to accept calls transferred thereto or to direct them to another position, the discrimination being made in a concentration circuit KONC which tests the condition of the switch at the wanted position. An incoming call is extended over a link circuit LF, PS, and transfer is effected under the control of a switching circuit OMST with which the concentration circuit is temporarily associated. On the occurrence of a call, line finder LF hunts, and test relay TR operates followed by DTR. The position selector PS now hunts for a position marked by idle potential in bank e and by ground in bank t1, and test relay PTR pulls up, followed by PHR. Switching relay COR operates and the calling lamp lights over wiper c in series with CR which energizes when the operator answers. In the case of an incoming toll call, ILR operates and the calling lamp is flashed by interrupter S25. Relay CR connects up OFR. If the call requires to be transferred to another position, the operator depresses her transfer key momentarily and sets up the number of the required position on her switch OS. Relay TER operates to ground over wiper d followed by TEIR, and CR, OFR release. The switching circuit OMST becomes associated over switch SM, test relay TR connects up DTR, FJR and CR1 operates in the link circuit to switch through. The a and b wires are connected respectively through SR1,4 and SR2,6 to 24 volts, SR1,2 being polarized by rectifiers and SR4,6 being marginal, and these wires may be connected over keys to 48 volts through a high or low resistance or to ground. The tens digit received by the SR relays is transferred to corresponding relays AR which lock over PAR. Relay AAR then pulls up, so that the received units digit is transferred to relays BR which lock over BBR. A cancel signal causes the operation of SDR which releases FJR to clear down the operated storage relays. The start signal causes the operation of SAR, which, provided two digits have been registered, connects up ISR. Relays RTR1,2 operate to seize the concentration circuit KONC provided it is idle, and OKR, OHR follow. The stored number is repeated to the concentration circuit, and if the call is to be transferred to the corresponding position, a circuit is made for OMR which releases the concentration circuit. Relay MTR energizes over a common resistance provided the marking multiple is free, followed by MXR and the position selector PS picks up first the tens marking and then the units marking applied to bank t2 by the AR and BR relays. Test relay LTR responds each time and finally connects up RKR, which operates J2R in the link circuit, whereupon the switching circuit is released. Test relay PTR energizes over bank e when the operator's position is idle, followed by PHR, JHR, ILR, and the calling lamp is flashed by interrupter S27. As before, CR, OFR pull up when the operator answers. If no number is received in the switching circuit or if OMR is not operated from the concentration circuit, alarm relay ALR2 energizes after a certain time and by means of relays VCR, VHR the number 99 is set up to direct the call to the supervisor. Concentration circuit, KONC. Relay RSR energizes in series with RTRI of the switching circuit, followed by UKR, COR1,2, CHR. Transfer relays TOR1,2,4,6 and EOR1,2,4,6 are connected in parallel with the corresponding storage relays of the switching circuit and take over the stored number. Assuming that the number is 19, the transfer relays bring about the operation of position relay PKR19 in series with FER, and PBR energizes if the position is staffed. Relay PKR19 connects the switch OS of position 19 to tens and units relays TCR, ECR and appropriate relays are energized over their left windings if the switch stands at normal (NN) or at the number of the position or over their right windings if the switch stands in any other position. The left windings are in series with own position relays EPR1,2 and the operation of both these relays and of PBR makes an immediate circuit for OMR in the switching circuit to transfer the call to position 19. The right windings of TER, ECR are in series with APR1,2 and the operation of either of these relays connects up FFR which energizes SDR in the switching circuit and COR1,2 to cancel the stored number, but PKR19 remains held. Relays LAR, CKR pull up and the number set up on the switch of position 19, say 12, which is registered on relays TCR, ECR is transferred to transfer relays TOR, EOR. Position relay PKR12 now energizes in place of PKR19 and a fresh test is made to ascertain the condition of the switch of position 12, and if necessary the operations are repeated until a position is found which enables EPR1,2 to energize. Relays OFR1,2, CKR now operate and the number registered on relays TOR, EOR is transferred to the switching circuit, after which FFR falls back and connects up OMR in the switching circuit. If a position is not staffed although the position switch is set to a transfer position, IBR energizes and brings about the operation of PKR99 to transfer the call to the supervisor.