Patent GB-257645-A (GB)
Title: Improvements in automatic and semi-automatic telephone systems
IPC: H04M3/22
Filed: 1925-05-04
Abstract: 257,645. Standard Telephones & Cables, Ltd., (formerly Western Electric Co., Ltd.), Searle, A. M., Baker, J. H. E., and Moscrip, W. R. May 4, 1925. Automatic and semi-automatic exchange systems ; metering. - A group selector is provided with eleventh rotary-step shaft-controlled springs, which when actuated, in addition to applying busy tone to the calling line and earthing the test-wiper to operate a traffic meter, short-circuit the switching relay to prevent its energization at this time. The invention is described as applied to a first code selector from which access is also had to a register-controller of the code-translating type. Provision is made for releasing the registering apparatus in the case of a permanent loop condition, or if the calling party delays dialling or only dials part of the wanted number, and for sending number-unobtainable tone if dialling is commenced before an idle register-controller is engaged. In the case of a call to an operator, release control is transferred to her when the calling party hangs up. First code selector. Upon the relay group shown being taken into use, line relay L responds over the calling loop, energizes release relay B, and closes a. circuit for impulse relay A over retard coil I and the right-hand winding of a polarized relay D, which, however, remains inert since its other winding is energized in opposition. Relay B grounds the test wire RT and energizes change-over relay C, which starts a register controller finder hunting. When an idle register-controller is engaged, relay K energizes, opens the finder stepping circuit, and completes an in-dialling circuit to the register-controller over the lower winding of relay L, the sub. scribers' loop and the pulse wine PU : the relay A is held over a loop in the register-controller. The wanted number is now dialled, and when the register-controller sends the first routing digit, the relapses of relay A energize the first code selector stepping magnet V, after the first step the change-over relay C being energized in parallel with the magnet V over contacts N4, 3, and the stepping relay G responding over con. tacts N1, 2 preparing the circuit of rotary mag. net R, and locking over interrupter springs W. At the end of these impulses, relay C relapses and closes the rotary stepping circuit. The relay G and the magnet R interact in the usual manner until an idle trunk is engaged, upon which a short-circuit is removed from the upper winding of switching relay H, which switches the registercontroller through to subsequent switches. When all the digits have been sent, the register-controller releases, and relay K relapses, switching through the talking circuit. Talking impedance is provided for the called party over retard I. Metering. When the called party replies, a current reversal over the back-bridge causes relay D to respond. Relay D earths the metering wire MW. Release. If the called party hangs up first, relay D relapses and earth returned over the meter wire MW lights a supervisory lamp SL. When the calling party hangs up relays L, B, D and H de-energize, the release-magnet Z is energized over a release alarm wire, and a homing circuit is completed for the register-controller finder. In the case of a call to an operator, release is under her control, relay B being held by battery on the lower line conductor when the calling party hangs up. All trunks busy; traffic metering. In the case of an 11th step busy condition cam springs S operate and apply busy tone over lead BY and condenser QA to the lower conductor. Cam springs S2, 3 ground the test wiper FP to actuate a traffic meter and short-circuit the operating winding of relay H to prevent its energization in series with the meter. Permanent loop condition; subscriber delays dialling. In either of these circumstances relays A, B, L, C, K are energized as before and after an interval ground is applied to the pulse wire P, V, causing the relapse of relays L, B and the energization of relay M. Relay M locks up, lights supervisory lamp SL and restores the circuit of relay L, which re-energizes relay B. When ground is removed from the pulse wire, the register-controller releases, relay K relapses, and relay A holds over retard I. In the second circumstance, if the subscriber dials, relays L, A will respond, the vertical magnet V will be energized and on the first vertical step relay H pulls up, locks over its lower winding in series with relay M and connects number unobtainable tone NU to the lower conductor. Relay H opens the circuit of relay A, and relay C relapses disconnecting the magnet V. When the subscriber hangs up, relays L, B, H, M de-energize and the switch is released. Subscriber dials before an idle register-controller is engaged. In this event relay K has not yet energized, and on the first relapse of relay A due to the falling off of relay L, relay M energizes in multiple with magnet V. The lamp SL is lighted and tone NU sent as in the previous paragraph. Subscriber dials partially. If no digits have been sent out from the register-controller, relays A, B, L, C, K are energized at the time, and the instant relay L relapses due to time alarm ground on the pulse wire PU, the circuit of relay A is opened in the register-controller, and the vertical magnet steps up the wipers. On the relapse of slow-release relay B, relay M responds and the short-circuit is removed from the upper winding of relay H which locks in series with relay M. A further ground is maintained on the holding wire RT by the relay C for a short period after the relapse of relay B. Relay M reconnects relay L to the calling loop and deenergizes relay C which closes the release circuit. In the normal position of the switch, relay B again energizes. Relays L, B, M, H are nowenergized, the lamp SL is lighted and tone NU is connected up. If the code digits have been sent out by the register-controller, relay H is energized at the time the pulse ground is applied to wire PU, but the subsequent operations are the same as those previously described. If an 11th step busy condition is encountered after the sending of the first code digit, and further if dialling is not completed, busy tone is given as described above until the time pulse is applied to the wire PU when relays H, M lock up as before and number unobtainable tone is substituted for the busy tone.