Patent GB-260022-A (GB)
Title: Improvements in automatic telephone systems
IPC: H04Q3/00
Filed: 1925-06-25
Abstract: 260,022. Standard Telephones & Cables, Ltd., (formerly Western Electric Co., Ltd.)., Searle, A. M., Baker, J. H. E., Chanter, A. J., and Moscrip, W. B. June 25, 1925. Automatic exchange systems.-Relates to systems in which release is normally under the control of the calling party, but when a connection is extended to an operator's position, on the calling loop being broken the release control is transferred to the operator. Three modifications are described with reference to a register-controller system in which the calling party is fed from the first code selector at which point also release is initiated. In the modifications illustrated in Figs. 1 and 3, the release relay B is held energized by the out-impulsing relay A which is maintained energized over a circuit extending over a back contact of the line relay and the positive speaking conductor to battery at the operator's position. In the arrangement shown in Fig. 2, the relay A is held by battery on the positive conductor when the operator answers, and on the calling party hanging up an, additional relay P locks under the control of relay A. opens the release circuit, and grounds the holding wire. First arrangement, Fig. 1. This is the same as the first code selector described in Specification 257,645 excepting the connections of the impulse relay A and the release relav B. On the energization of the line relay L when the first code selector is taken into use, relay A energizes over its upper winding, the relay I and the righthand winding of polarized relay D, to earth at armature 12 of relay H. Whilst the registercontroller is connected up during the energization ot relay K, this circuit for relay A is extended to a loop in the register-controller. In the event of the call being extended to an operator, no loop is found at her position, but battery is connected to the positive wire. The relay I thereupon relapses and closes a circuit H17, 18, L9, 11, M14, 15 for the upper winding of relay A. If now the calling party hangs up, the relay L relapses, and a holding circuit is closed over the lower winding of relay A, from earth at contacts 14, 15 of relay M to battery on the positive wire : the current in this circuit may also operate an operator's supervisory signal. The relay A remains energized as long as battery is applied to the positive wire at the operator's position, and holds the release relay B energized at contacts 8, 9 after its circuit has been opened by relay L, thus giving release control to the operator. Second arrangement, Fig. 2. In this system the retard I is dispensed with, the impulse relay A providing the necessary balanced impedance during conversation. Also an additional relay P is provided for holding open the release circuit and earthing the release wire RT when the connection is held from an operator's position. When the code selector is taken into use, the impulse relay A energizes in a circuit including earth and battery at the inner armatures of relay H and the right-hand winding of relay D. Whilst the register-controller is connected up and relay K is energized, the relay A is held over a loop in the register-controller. On the cessation of the first impulse series sent from the registercontroller, the change-over relay C relapses and relay P is energized over the homing wiper HW and contact HE in series with the stepping magnet DM of the register-controller finder. Relay P short-circuits the lower winding of relay A which releases. When an idle trunk is engaged, relav H extends the impulse circuit to the next switch. At the completion of the set-up, relay K relapses and de-energizes relay P, therebv restoring the circuit of relay A which energizes in series with the right-hand winding of relay D and forms a back-bridge. In the event of the call being routed to an operator, the relays D, A will be de-energized, and on the calling party hanging up between the relapse of relays L and B, relay P will energize, and on the relapse of relay B close a circuit for the lower winding of relay A, from earth at armature 9 of relay B to battery on the positive wire : current in this circuit may be used to give a supervisory signal. Relay P will now be held over armature 8 of relay A and will hold the circuit of the release magnet Z open and the release wire RT grounded as long as relay A is maintained energized by battery on the positive wire from the operator's position. Other operations are similar to those of the arrangement described in the previously-mentioned Specification. Third arrangement, Fig. 3. In this, as in the first arrangement, when the call is routed to an operator and the calling party hangs up, the impulse relay A is energized over the positive wire and holds the release relav B : the detailed circuits, however, are somewhat different. The response of the line relay L energizes the impulse relay A over the usual circuit including the retard relay I. Relay A completes a circuit H15, L6 for release relay B, which prepares the first code selector and causes the register-controller finder to hunt. When an idle registercontroller is engaged, relay K pulls up, extends the dialling-in circuit over wiper PE to the A digit switch, and completes an out-impulsing circuit for the upper winding of relay A over a loop in the register-controller. On the receipt of the first routing digit, the vertical magnet V is energized, and series relay C closes a circuit for relay G. On the relapse of relay C, the rotary magnet R is energized and thereafter interacts in the usual manner with relay G until an idle trunk is engaged, when switching relay H pulls up, de-energizes relay A and extends the outimpulsing circuit to the next switch. When the set-up is completed, relay K relapses, completes the talking circuit, and closes a back-bridge over the relay I. If the calling party hangs up first, the relapse of relay L short-circuits the lower winding of relay I to render it slow-torelease, opens the circuit of relay B, and energizes the lower windings of relays M, A. Relay M locks to the release trunk RT and de-energizes relay A. The relapse of relay B a moment later energizes the release magnet Z and de-energizes relay M. Should the called party hang up first, the current reversal over the back-bridge causes the relapse of relay D and earth returned over the meter wire MW lights a lamp over wire SU. If the subscriber dials before an idle registercontroller is found and relay K is energized, the first code selector is stepped up and when relay L falls away for the second impulse, the relay M energizes over off-normal contacts N5, 6, locks over its upper winding and opens the driving circuit of the register-controller finder. When relay A relapses for the second time, relay G operates and locks, and connects number unobtainable tone NU to the lower conductor. If the subscriber omits to dial, time pulse ground on the wiper PE short-circuits the lower winding of relay L, which de-energizes relay B, which in turn energizes relay M over its upper winding. Relay M locks up and remakes the circuit of relay L over the subscriber's loop : relay B again energizes. Should the subscriber now dial, on the first relapse of relay A, the relay G locks energized and applies NU tone to the calling line. In the event of partial dialling by the subscriber, or of failure of the register-controller, time pulse ground on the wiper PE de-energizes relays L, B and energizes relay M. The relapse of relay B energizes the release magnet Z, and the relay G pulls up and applies NU tone. When the pulse ground is removed from wiper PE, relays L, I, B again energize. Release is effected as before. When the call is routed to an operator, the relays I, D are not energized and when the calling party hangs up relay R is energized over its lower winding to battery on the positive wire, and maintains the release relay B energized. A supervisory lamp may be included in the last-mentioned circuit of relay A. In some cases it may be arranged that when the operator withdraws her plug battery is replaced by ground on the lower conductor. The characteristics of the relay A are such that it will release in spite of different ground potentials at the two exchanges.