Patent GB-257616-A (GB)
Title: Improvements relating to automatic and semi-automatic telephone exchange systems
IPC: H04Q3/00
Filed: 1926-08-26
Abstract: 257,616. Siemens Bros. & Co., Ltd. Aug. 31, 1925, [Convention date]. Automatic and semi-automatic exchange systems.-In a system in which long-distance calls are offered over the same connectors that are used for ordinary calls, a signal indicating that the call is a long-distance one is forwarded to the connector over the a-wires of the connection, and a signal indicating that the wanted line is busy is sent back to the trunk operator's supervisory lamp over the same wires. Impulsing takes place over the b-wires. In a call from a trunk operator, as long as dialling is in progress battery poten tial is connected by relay Q, Fig. 1, to the awire of the outgoing trunk and energizes relays Q, QA, Fig. 2, in the incoming selector to apply half-battery potential to the a-wire of the connector, Fig. 3. When dialling is finished these potentials are removed and ground-connected signal-back relays Y, Fig. 1, Y, Fig. 2, are connected to the a-wires for supervisory purposes. If the wanted line is idle, ringing current is supplied in the ordinary way from the connector and ringing tone is sent back, and on the reply of the subscriber the connection is switched through at the connector and relay Y, Fig. 2, is energized over the called loop and energizes relay Y, Fig. 1, over the trunk a-wire to extinguish the cord lamp SL. If on the other hand the wanted line tests busy, the ground-connected first winding of a relay TL, Fig. 3, is energized from the a-wire while there is still half-battery potential on this wire. The relay TL keeps the test circuit of the busy line closed (normally it is closed only for a moment), disables the ringing relay, prepares a circuit for talking in on the busy line through condensers, and locks its battery-con. nected second winding to the a-wire, so that when the relay Y, Fig. 2, is connected to this wire a moment later it is energized and energizes relay Y, Fig. 1, to extinguish the lamp SL. The operator takes this, in conjunction with the non- arrival of ringing tone, as a signal that the line is busy, and asks the parties to hang up. As soon as the line is cleared the test relay becomes energized and the a and b wires in the connector are switched metalically through to the wipers, the relay TL being disconnected from the a-wire so that relay Y, Fig. 2, is de-energized and the lamp SL lights up. The operator now momentarily energizes relay Q, Fig. 1, to apply battery to the trunk a-wire, which initiates the supply of ringing current from the incoming selector, Fig. 2. Ringing is tripped when the subscriber answers, and relay Y, Fig. 2, is energized over the called loop to extinguish the cord lamp. The circuits are arranged to permit re-ringing in the same manner. Modified connectors are described for serving private branch exchanges and party lines. In the following description (excepting one paragraph) it is assumed that the connection includes only the selector, Fig. 2, and connector, Fig. 3, but it is to be understood that it may include incoming selectors at intermediate exchanges, which repeat the signals in the same manner as the selector shown in Fig. 2. Outgoing trunk circuit, Fig. 1. When the operator plugs in, relays G, J are energized and battery is connected to the b-wire. The operator throws a master dial key K and a cord dial key KK to energize relay A in a circuit including the impulse springs 1. On the return of dial tone the operator dials the wanted number, which is repeated by relay A over the b-wire, relay D becoming energized at the first movement of the dial and locking in series with relay Q which removes a short-circuit from the impulse repeating contact a1 and connects the battery to the a-wire. As soon as she has finished dialling the operator restores the keys K, KK and relays A, Q relapse. Incoming selector, Fig. 2. Relay A (1) is energized over the b-wire and energizes relays V, D, and relay Q is energized over the a-wire as soon as dialling commences. The first digit is repeated in a circuit a1, VM, q2, d2, t5. The offnormal contacts k1, k2, k3 are shifted, relay L is energized (a2, d1, k3, v1) and locks up, and D is held over a2, d1, k3, v1. At the end of the digit relay D relapses and closes the circuit of the rotary magnet RM. On finding an idle trunk, relay T is energized over winding 1 and the test-wiper, locks over winding 2, grounds the test-wiper, and switches through. Relay B is energized in series with the line relay of the next switch over the outgoing b-wire and energizes QA (b1, q3, tr2, tl, d1 k3, v1) which connects half-battery potential to the outgoing a-wire. Further digits are repeated at contact a3. Connector, Fig. 3. Relay N is energized over the incoming test wire and the impulse relay A is energized over the incoming b-wire and energizes D (t1 n4, D, a2, k3, w1). The tens digit is repeated in a circuit d2, a1, g2, VM. The vertical off-normal contacts k1 k2, k3 are shifted and relay D is held over a2, d3, but relapses at the end of the digit and energizes relay G (t1, n4, G, tl1, d1, k3, w1) which again energizes D which closes a locking circuit for G. The units digit is repeated in a circuit d2, a1 g2, RM. The rotary off-normal contacts w1, w2 are shifted and relay D is held over a2, d3. At the end of the digit, relays D, G relapse in turn, and in. the interval a test circuit n3, T (1, 2), g3, d2 is closed. Wanted line free; automatic supply of ringing current from connector. If the line is free, relay T, Fig. 3, is energized and disconnects the impulse relay A, which short-circuits a winding of relay TR and removes a short-circuit from relay S, which becomes energized (d2, g3, S, a3, tr1, w1) and supplies ringing current from a source RG over relay TR (2). Ringing tone RS is connected to the incoming a-wire and the operator restores her dialling keys, de-energizing relays A, Q, Fig. 1, and Q, QA, Fig. 2, so that the signal-back relays Y, Fig. 1, and Y, Fig. 2, are connected to the a-wires. The subscriber's answer energizes relay TR, which locks over its upper winding and short-circuits the ringing relay Y, Fig. 2, in series with relay B over the called line. Relay Y unlocks relay L and connects the upper winding of relay A to the incoming a-wire. This energizes relay Y, Fig. 1, which cuts resistance JA into the cord sleeve circuit to de-energize the marginal relay G and extinguish the lamp SL. Wanted line busy; operator breaks in. If the line is busy, relay T, Fig. 3, does not energize, and if the call had been from an automatic subscriber the succeeding relapse of relay G would energize relay TR (d2, g3, a3, TR (1) w1) to short-circuit the ringing relay S and connect up busy tone BB. But in the present case, the call being from an operator and the operator not having yet had time to restore her dialling keys, there is half-battery potential on the incoming awire, and the non-energization of relay T results in the energization of relay TL (a-wire, s2, t2, tr2, tl4, TL (1), d4, g1) which locks itself to the a-wire through its second winding (TL (2), tl6, tr2, tl2) and locks relay G to keep the test circuit closed. When the operator restores her keys, relays Q, Fig. 1, and Q, QA, Fig. 2, relapse and relay R is energized (qa3, R, s6, q3, tr2, t1, d1, k3, v1). Relay Q, Fig. 2, connects relay Y to the a-wire, energizing it in series with TL (2), Fig. 3. Relay Y causes the lamp SL to be extinguished as before, and the operator speaks with the busy line and ask the parties to hang up. As soon as the line is cleared, relay T becomes energized, unlocks relay G, and switches the talking circuit metalically through. The relapse of G energizes TR (d2, g3, a3, TR (1), w1) which unlocks TL, which disconnects A The ringing relay S which until now was short-circuited by relay A is short-circuited at tr1, and relay TR is locked at the same contact. The awire being now disconnected from TL (2), relay Y, Fig. 2, relapses and the lamp SL lights up. Supply of ringing current from incoming selector initiated by operator; re-ringing. The operator momentarily throws the Keys KK, RK to energize relays A, Q, Fig. 1, and battery connected at q2 to the a-wire energizes relay S(1), Fig. 2, over y2, rl. Relay S locks over its second winding (tr1, t1, d1, k3, v1) by opening a shortcircuit at s5, de-energizes R, and supplies ring- ing current from a source RG over TR (2). Ring- ing tone is sent back from RS. The subscriber's reply energizes relay TR which short-circuits S(2) at tr1. The relapse of relay S open-circuits TR (2) and short-circuits TR(1). Relay R is again energized and connects S(1) to the a-wire to permit re-ringing. Relay Y is energized over the called line and extinguishes the lamp SL. Supply of ringing current from the incoming selector of a further exchange. On the energization of the ringing relay S, Fig. 2, battery is momentarily connected over qa1, r2, s2 to the outgoing a-wire to initiate ringing from the incoming selector at the further exchange, and relay TR (2) is energized over the b-wire in series with the impulse relay at the further exchange to trip the ringing at the first exchange. Release. The called line is fed through relays B, Y, Fig. 2, and the relapse of Y when the line is opened extinguishes the operator's lamp SL. The operator withdraws the plug, releasing relays A, V, T, Fig. 2, and the release magnet MM is energized. The opening of contact t4 de-energizes relay N, Fig. 3, which unlocks relay T to energize the release magnet MM. Relay N is not re-connected to the incoming test-wire, to mark the connector selectable, until the normal contact k1 is closed. Modified connector, Fig. 4, for calls to private branch exchanges. The circuits are substantially as in Fig. 3 apart from the addition of relays TX, PR, of which TX is only energized on trunk calls and PR only if the connector is set on the busy first line of a P.B.X. group. The principle employed in dealin