Patent GB-257685-A (GB)
Title: Improvements relating to automatic telephone systems
IPC: H04Q3/00
Filed: 1925-06-10
Abstract: 257,685. Siemens Bros. & Co., Ltd., Berry, J., and Patterson, W. G June 10, 1925. Automatic exchange systems; metering.-In a system in which release is normally under the control of the calling party, a call is held from a manual operator's position by the sending therefrom, on the calling party hanging up, of a signal identical with the normal answering supervisory signal given in a purely automatic connection. The replacement of the calling party's receiver also effects circuit changes to prevent metering. The invention is described as applied to a system in which dialling impulses are sent over the b wire and the supervisory signal returned over the a wire, and to a registercontroller system using loop impulsing and reverse battery supervision. In the first case an additional relay, which when energized holds up the release relay, is connected in series with the usual supervisory relay to the a wire, and arrangements are provided whereby when the calling subscriber's receiver is removed, the additional holding relay is short-circuited and when it is replaced the supervisory relay is shortcircuited. In the second system an additional relay is arranged in series with the usual bridged supervisory relay. When the calling party hangs up after calling a manual operator, the additional relay relapses and causes a holding circuit to be prepared for the dialling relay, which is locked up by the relapse of the supervisory relay on the return of the normal supervisory signal, and maintains an alternative ground on the holding wire. First system, Figs. 1, 2 and 3. Calls are extended in the usual manner over a first selector. Fig. 1, and an incoming selector, Fig. 2, to another automatic subscriber or to an operator's position, Fig. 3, dialling impulses being sent over the b wire and the supervisory signal over the a wire. At the first and incoming selectors, a special holding relay H is connected in series with the usual supervisory relay Y to the a wire, the relay H being short-circuited when the impulse relay A is energized and the relay Y being short-circuited when the relay A is de-energized. In the case of a call to an automatic subscriber, when the called party replies, the relay Y, Fig. 2, at the incoming selector energizes over the called loop and connects battery to the incoming a wire, causing the response of the supervisory relay Y, Fig. 1, at the first selector, and initiating the usual metering operations. Relay Y de-energizes relay L which opens the holding circuit of relay V so that if the calling party clears first, although relay H may operate, the connection is not held. When the call is extended to an operator's position, Fig. 3, the a wire is found open but a relay U across the lower talking condenser, operates from battery on the b wire, removes a shunt from the upper condenser, connects a ringing signal over wire RS to the incoming line, and lights the calling lamp CL. On the operator plugging in, the relay U is held by earth on the tip, and cut-off relay CO energizes in series with sleeve relay SL, thereby cutting out the ringing signal and the calling lamp CL, and lighting a supervisory lamp FL. When the calling party hangs up, the impulse relays A relapse and the supervisory relays Y are short-circuited in place of the holding relays H. The opening of the b wire to the operator's position de-energizes relay U, and battery over a relay R is connected to the a wire, this time energizing the holding relay H at the incoming selector, Fig. 2. Relay H closes a holding circuit for the release relay V and connects battery to the incoming a wire, thereby energizing relay H and holding the release relay V at the first selector, Fig. 1. Relay R opens the circuit of the lamp FL. Release is now under the control of the operator. In selectors in which the dialling relay D responds to all series of impulses, and therefore energizes when the caller hangs up, this relay may be utilized to short-circuit the relay Y or the relay H according to whether it is energized or de-energized. Second system, Figs. 4, 5 and 6. In this application loop impulsing and reverse battery supervision is employed in a system employing register-controllers. A call is extended over a first code selector, Fig. 4, giving access to local switches or to a repeater, Fig. 5, and a junction over which access is had to another automatic subscriber or to a manual operator's position, Fig. 6. Only such control and supervisory relays as are necessary for an understanding of the invention are shown in Fig. 4, the circuit to and from the register-controller being similar to those described in Specification 256,697, and being omitted for simplicity. When the code selector is seized, circuits are closed for the line relay L, Fig. 4, the release relay B, and a metering control relay H which locks over its armature. Both windings of a high impedance relay I and the left-hand winding of a polarized supervisory relay D are bridged across the outgoing conductors. The polarizing right-hand winding of relay D is energized bv relay B. The impulses received by relay L are repeated to the registercontroller, the dialling relay C responding during the impulse trains and short-circuiting the righthand winding of relay I. In response to the first digit sent from the register-controller, the code selector is stepped up, and then finds an idle link. say to the repeater, Fig. 5, whereupon the test relav T responds in the usual manner. The high-impedance relay I, Fig. 4, now energizes over the windings of the repeater line relay A, Fig. 5, the response of which causs the energization in turn of metering relay H, release relay B, and the right-hand polarizing winding of supervisory relay D, and bridges both windings of relay I and the left-hand winding of relay D across the outgoing trunk. Relay B locks up and closes a holding circuit for relay H. During impulsing, C is energized and connects a low-impedance bridge a3, c3, b3 across the outgoing wires. If the call is to another automatic subscriber his reply reverses the current over the back bridge and relay D is energized as well as the relay I, the relay H is unlocked, and current is reversed in the back bridge at the code selector, Fig. 4. The polarized relay D at this switch now responds with the relay I, and the metering relay H is unlocked and after a short interval the metering wire m is grounded over contacts d1, h2. Release is under the control of the calling party, the relapse of release relay B opening the circuit of the dialling relay C and removing ground from the holding wire, c. In the case of a call to an operator's position, Fig. 6, battery is found on the a-wire, whilst the b-wire is earthed over the secondary winding of a ringing signal transformer, the wire RS, and relay U. The relay U which is shunted by a condenser to by-pass speech currents, energizes relay UA, which lights a calling lamp CL. A ringing signal is sent back over the b-wire. When the operator plugs in, cut-off relay S and sleeve relay SL pull up, disconnect the signal and lamp CL, and light lamp FL. The a- and b-wires are now connected to battery and earth respectively over the cord circuit relays R, T, the former of which cuts out the lamp FL. In this condition the relays I at the code selector and the repeater are operated and the relays D are unoperated. If the calling party hangs up, the line relays L, A relapse, the b-wire is opened, and the relays U, R, UA de-energize, the latter reversing the battery connection to send back the normal supervisory signal. The lamp FL is lighted. At the repeater, Fig. 5, relay A opens the junction back-bridge, relay I relapses, and between the relapse of re1ays A and B the dialling relay C is energized. Relay H locks over contacts c4, h1 and prepares a holding circuit for relay c. When relay B has fallen away, relay C de-energizes, but before it falls away the current reversal from the operator's position causes earth to be applied to the a-wire, and the supervisory relay D energizes over its windings in series in a circuit b4, a2, c2, closing a locking circuit d4, h1 for relay C, which at contact c1 applies alternative holding earth to the c-wire. Relay D reverses the battery and earth connections to the incoming trunk. At the code selector, Fig. 4, the de-energization of the line relay L is followed in a similar manner by the relapse of relays I, B and the response of relay C. Relay H is then held over contacts c3, i1 and prepares to hold relay C. Before relay C falls away ducts, its circuit being opened bv relay B, it is locked' up over contacts h2, d1 by the response of relay D, which energizes over both its windings in series to the a-wire, which is earthed when current is reversed at the repeater, Fig. 5. The connection is now held bv alternative earth on the c-wire applied at contact c<1> and release is under the control of the operator. The relay H keeps the metering circuit open. If the calling party again removes his receiver, the circuits return to their previous condition and the lamp FL is extinguished.