Patent GB-433158-A (GB)
Title: Improvements relating to the control of selecting switches of the kind used in automatic telephone and other selective systems
IPC: H04Q1/32
Filed: 1934-03-01
Abstract: 433,158. Automatic exchange systems. SIEMENS BROS. & CO., Ltd., Caxton House, Tothill Street, and HUMPHRIES, H. E., 61, Rochester Way, Blackheath, both in London. March 1, 1934, No. 6569. [Class 40 (iv)] The stepping of a reverse-drive switch in response to impulses is effected by a selfinterrupting circuit which is governed by an independent circuit or circuits for the magnet over an impulse contact.. The switch may be arranged to take either one or two steps per impulse. Figs. 1, 2 show a first selector and common control circuit which are generally similar to those described in Specification 428,622, (Figs. 3 and 4), the digit switch DS marking the group to be searched after responding to one or two digits. Dialling relay C operates at the first impulse and closes a self interrupting circuit for the magnet DSM, while an independent circuit for the latter is made at each impulse over back contact a2. The switch DS therefore advances one step each time line relay A pulls up. According to the setting of the switch, one of terminals TE 1-8 is marked over bank DS1, and one or more relays are operated to determine the subsequent operation. In the case of terminals TE 1-4, relay R operates and initiates immediate hunting of the selector. In the case of terminals TE 5-7, however, SD operates and advances the switch DS to a subnormal position 11 or 12, dependent on the condition of relay Y, in order to take a second digit. If relay PA is not operated, in which case 7 is also back, the switch DS takes one step per impulse in the same manner as for the first digit. If, on the other hand, PA is operated, two circuits for the magnet DSM are completed alternately over front and back contacts a2 and odd and even terminals of bank DS4, the self interrupting circuit being made at the first impulse as before, so that two steps are taken per impulse. One of terminals TE 1-4 is marked over bank DS1 or DS2 after the second digit, and relay R initiates the hunting operation. The operation of PP, PA after the first digit brings about the advance of the selector through 180‹ to a subnormal position and substitutes wipers DS 2, 6, 8 for wipers DS 1, 5, 7, while Y, S after either digit may control respectively wiper-switching and transmission of a discriminating signal. Relay BT energizes over the metering wire except in the case of a restricted service subscriber. On a call to an operator (first digit O), relay R initiates hunting and if BT is back S also energizes to indicate to the operator the nature of the calling party. Terminal TE9 provides for routing to an operator in the case of certain first digits or digit combinations, while TE8 is used for spare digits. The markings applied over banks DS5, 6, may be made dependent on the condition of relay BT. In the modification shown in Fig. 3, dialling relay C operates immediately upon seizure, completing the self interrupting circuit for the magnet DSM, which has an independent circuit at each impulse over front contact a1. The switch therefore advances one step each time line relay A falls back, and a final step when C relapses at the end of the train.