Patent GB-242048-A (GB)
Title: Improvements relating to automatic telephone systems and the like
IPC: H04Q3/00
Filed: 1924-10-01
Abstract: 242,048. Siemens Bros. & Co., Ltd., and Patterson, W. G. Oct. 1, 1924. Automatic exchange systems.-If at any stagea selector fails to find an idle trunk or if the wanted party is busy, all the selectors are released and the line switch advances to its last '.terminals from which it sends busy tone. The invention is described in connection with calls within an exchange, calls from a manual to an automatic exchange and calls between automatic exchanges. Release is under control of a relay in the first or incoming selector and while the connection is being set up this relay is controlled by a " busy relay " which also provides battery feed connected to the outgoing p-wire and energized in series with the impulse relay of successive switches in the chain over a contact of the first selector line relay. When the called party replies, sole control of release is restored to the calling party. If a dead level is dialled the wipers move to 11th terminals to send " number unobtainable " tone and the release of the connection is prevented until the call is abandoned. Line-switch and busy-tone arrangements, Fig. 1. The switch is of the kind described in Specification 241,655 in which after the operation of the cut-off relay, one of its contacts t' is held operated (i.e. open) by a latch p until the wipers move on to their final terminals. Line relay R starts the stepping magnet over wiper Do in its normal position and the driving circuit is maintained over the off-normal arc until the cut-off relay T pulls up over a winding of the line relay of an idle first selector. Relay T locks up over its low resistance winding 1 to the outgoing cwire. In the case of normal release, the relapse of relay T causes the wipers to be driven on to normal. In the case of busy release. however the re-energization of the line relay causes relay T to stop the switch on its last terminals since the latch p is tripped in this position. Busy tone is sent back from BB and holds up the line relay until the subscriber hangs up whereupon the relapse of relay T allows the switch to be driven to normal. First selector, Fig. 2. Line relay A which is first energized over its winding 3 and the c-wire and subsequently over its windings 1, 2 and the loop, energizes release relay V which sends back holding battery for the cut-off relay, Fig. 1, and energizes relay D to send back dialling tone from DS. The first digit is repeated to the vertical magnet VM over a<1>, d<2>, t<5>. The change over of vertical springs k<1> - - k<3> energizes relay L which locks up and arranges for the relapse at the end of the digit, of relay D, to complete an interrupter circuit for the rotary magnet RM. When an idle line is found, test relay T pulls up over its winding 1 and the c-wiper, grounds the latter and locks up over its winding 2 and gives control of the release relay V to " busy relay " B which is hereafter energized in series with the impulse relay of the most recently seized selector over a contact of relay A. Subsequent digits are repeated by relay A, relay D pulling up at the beginning and falling back at the end of each digit to control the switch over. When the called party replies, the operation of the supervisory relay Y releases relay L to restore the sole control of relay V to the calling line. In the case of calls to a manual board a small current over the a-wire insufficient to operate relay Y energizes relay H to make release of relay V independent of relay B. When relay V does fall back it disconnects the incoming c-wire and releases T which takes ground off the outgoing c-wire and energizes the release magnet MM. Busy release. If the first selector fails to find an idle line in a live level it moves to 11th terminals and the springs w<1> change over. Relay T pulls up in a circuit v<3>, T(2), w' T(1), l<2>, and completes a circuit H, Y, A<o>, LL, in which H and Y do not pull up. Relay LC locks up over a key K and lights a lamp J. The b-terminal being dead, relay B falls back and is followed by the release relay V. NU tone arrangements. When the wipers are raised to a dead level they move to 11th terminals. Relay T pulls up, as in the case of busy release, over contact w<1> but in this case the b-terminal is connected to ground and relay B is therefore held up until the call is abandoned in response to a tone signal sent back from NU over the a-wire. Two-relay group selector, Fig. 3. Impulse relay A on being energized over the " busy relay " in the first selector energizes relay T in series with the vertical magnet V M (which is not operated) over, w<1>, a<1>, k<3>, w<2>, T(1). Relay T locks up over t<5>, k<3>, w<2>, and relay A repeats the digit over a<1>, w<1>, t<6> to the vertical magnet V M. The change over of vertical springs k<1> - - k<3>, connects relay T (1) to the a-wire instead of to battery at t<5>, and when at the end of the digit, relay D at the first selector falls back relay T falls back also and makes the rotary circuit over a<2>, k<2>, t<6>. Rotary springs w<1> - - w<3> change over, and when an idle line is found relay T pulls up over its winding 1, connects the incoming to the outgoing c-wire, looks up over its two windings-in series and casts off relav A. Busy release and NU tone are arranged for as in the first selector, contact w<4> corresponding to contact w<1> in Fig. 2. Connector, Fig. 4. Relay N pulls up over, and' locks itself to, the c-wire and impulse relay A pulls up over the busy relay in the first selector and energizes relay D over n<4>, D, a<2>, k<3>, w<1>. The tens digit is repeated over d<2>, a<1>, g<2> to the vertical magnet V M and vertical springs k<1> - - k<3> change over to arrange for the relapse of relay D and consequent energization of relay G at the end of the digit. Relay G switches the impulse circuit over to the rotary magnet R M and re-energizes relay D. Owing to the change over of rotary springs w<1>, w<2>, relay D falls back at the end of the digit and releases relay G. Supply of ringing current. If the line is idle the relapse of relay D energizes the switching relav T over d<3>, g<3> T (2) (1) n<3>, ground at the line switch Relay T locks up over its winding T, and cuts off relay A, but the " busy relay " is held by ground at g<5> over t<3>. After an interval relay G falls back and energizes relay S which puts another ground on the incoming b-wire to hold the busy relay and act as a return for ringing signal from RS which it connects to the a-wire. Ringing current is sent out over relay TR which operates when the called party replies and short circuits relay S whereupon the supervisory relay in the first selector pulls up as previously described. Busy release. Relays D, G, fall in succession but relay T fails to cut off relay A which maintains a short circuit on relay S. Relay TR pulls up over a<3>, T R (2), w<2>, g<1>, and cuts off relay A to release the " busy relay " and makes an alternative short circuit for relay S. Relay N is released by the preceding switches and relay T completes the circuit for the release magnet MM. Inter-exchange working-manual to automatic. Trunks incoming from a manual office terminate in switches such as that shown in Fig. 5. This is the same as the subscribers line switch already decribed except that it has only one outlet and the trunk is permanently connected to the talking wipers. Actually two terminals are provided for the speaking position to guard against the possibility of split impulses. The incoming selector, Fig. 6, is, on the outgoing side of the bridge, the same as the first selector shown in Fig. 2. The line relay A however is impulsed over the b-wire alone. To guard against accidental impulses the circuit of the vertical magnet VM is held open at q<1> until the operation of relay Q over the awire when the dialling key is thrown. In the case of calls to a manual board relay H operates without relay Y, and sends back a signal over the a-wire, thus operating relay H A which renders the release relay V independent of the calling line until the operation of the answering supervisory relay Y. Inter-exchange working - automatic to automatic. The trunks terminate directly in incoming selectors, Fig. 7. The selector is seized and controlled over the b-wire relay A having only one winding. Relay Q is omitted. Otherwise the selector is the same as that shown in Fig. 6. The outgoing repeater at the distant office has a battery feed " busy relay " similar to that in the first and incoming selectors. Metering systems. The operation of the answering supervisory relay Y, Fig. 2 sends a metering impulse over A (3), y<2>, l<5> and releases relay L which opens the metering circuit. Specification 203,759 is referred to in the Provisional Specification.