Patent GB-316912-A (GB)
Abstract: 316,912. Standard Telephones & Cables, Ltd., Baker, J. H. E., and Wright, E. P. G. May 3, 1928. Automatic exchange systems.-In a registercontrolled system having revertively controlled single-motion selectors with contacts arranged in groups, the reverting impulses at each stage are sent by a relav which is connected to certain contacts in a 'control bank of the selector and opens a. loop extending from the selector to the register-controller. In the group selector, this relay is connected to the last contact of each group, but in the case of the final selector it is connected to the penultinate contact of each group and when this contact of the group preceding the wanted group is reached, circuit changes are effected to connect the relay to all contacts of the control bank. The number of lines in a group may be readily varied by altering the connections of the relay to the control bank, and the number of lines in a group may be different in different parts of the bank. When a second group or subsequent selector is seized, its operation is initiated by a relay energized over a loop in the registercontroller which is immediately replaced by battery and ground connection to the above mentioned loop at the selector. During group selection, a selector steps in a self-interrupting circuit over the contacts of each group, this circuit being opened when a reverting impulse is sent. The register-controller then sends an impulse to the selector to move it on to first contacts of the next group. At the end of the group selecting movement, the loop at the selector is replaced by the loop at the register-controller to initiate the hunting or final selecting movement. For the latter movement the loop in the final selector is immediately replaced. In the system described, the groups of selectors are controlled by temporarily used common relay groups including the relay which sends the reverting impulses. In the case of the first code selectors, this reverting impulse relay and other common relays are included in the register-controller. The connection between a selector and its common control group is completed by an individual relay when the selector is seized. A group of inter-exchange junctions having access to a group of incoming selectors controlled by a common relay group, is marked busy over a common third wire until the common relays of the incoming selectors are disengaged. If a busy condition is encountered at any stage, all switches subsequent to the first code selector are released and the busy signal is given from that selector. Specifications 276,067, 276,442, 295,448, 295,450, and 312,120 are referred to. Seizure of first code selector, Fig. 1; registration of digits. The non-numerical switching arrangements, which may be as described in Specification 295,450, have access to the first code selector only if the register-controller, Fig. 2, is free. If this is the case, relays BR, Fig. 2, and K, Fig. 1, pull up in series over the test wire. Relay K connects up the leads from the register-controller, and BR energizes RF which prepares the circuits for the registers and energizes' the back stroke magnet of the control switch SC. Impulse relay L pulls up, release relay B energizes and, the impulses are repeated over LI, PU, relay IR and distributor DD to register magnet AC, and IR pulls up during the train to energize magnet DDM which stops DD when IR falls back. The trains of impulses are thus sent to the register magnets AM - - EM in succession. Operation of first code selector. As soon as the first digit has been registered, magnet RM, Fig. 1, energizes in a circuit including DD1, SC1 and ground at H3, Fig. 1, and the selector takes one step. Reverting impulse relay ER, Fig. 2, pulls up over bank C of the selector to ground at H5, opens the circuit of RM, and energizes HR (lower) which locks up over its upper winding, interrupter springs of AM, and SC2. Magnet AM energizes over SC4, HR4. AR2 and releases HR which releases AM and the A register takes one step. When HR energized, relays CR PR, P and MD followed in turn, PR being locked to ground at B4, Fig. 1. Magnet RM now operates over CR1, ER1 and the previously indicated circuit, and the selector steps on to the first contacts of the first group so that ER fall back and is followed by CR which again completes a circuit for RM, and the selector is stepped, in a selfinterrupting circuit, on to the last contacts of the group. Relay ER re-energizes and repeats the operation for stepping the A register, moving the selector to the first contacts of the next group, and completing a self-interrupting circuit for magnet RM. When the register is on its last contacts, the next energization of HR completes a circuit (A2, SC4, HR4, AR2) for GR (lower) which substitutes ground at GR3 for ground from H3 over GR5 to operate the magnet RM so that the selector steps on to the first contacts of the desired group. The A register is stepped on to its first contacts by the energization HR, and when HR, ER full back, GR (upper) holds over JT2, PR5, ER2 to ground at BR2. The selector now hunts for an idle outlet in the group and when this is found, test relay H (upper) pulls up in a circuit from ground at CR7, Fig. 2 over GR8 to battery on the test wire. Relays JT and DR were looped across the line by GR, and JT now energizes as will be described later. If the selector proceeds to the last contacts of the group, ER energizes as before and opens the circuit of GR but, before this relay falls back, a circuit is completed for busy relay BF, Fig. 1. This relay is slow to operate so that if the last line is free, H operates and JT releases ER which opens the circuit of BF. If the last line is busy BF energizes locks to ground at MD6 and connects up busy tone lead BT. Relay K falls back and releases the register but MD holds over B1. Second group selector, Fig. 3. This selector has only two individual relays, namely, KG which connects up the common control relays, and the test relay HG. Relays BG, KG energize over the test wire when the selector is seized, battery over GG and ground from DG4 being connected to the negative and positive wires. Relay GG operates in series with JT in the loop in the register-controller, locks up over GG1, and operates CG and DG in turn, the positive wire being now grounded at GG2. The control switch SO has been stepped to position 2 by the energization of relay GR. If the next digit has not been registered GR remains energized over DD3 (position 2) although its holding circuit has been opened bv JT. When GR falls back, the loop over JT, DR is disconnected and replaced by battery and ground over the windings of AR while, at the selector, GG relapses and replaces the feed by a loop over AG which energizes in series with AR, the latter locking up over AR2. Relay HR (upper) energizes over AR1, interrupter springs of magnet BM and SC2 and holds over HR1 independently of AR. Relay AG in the selector holds CG and DG, magnet RM moves the switch one step, and relay EG pulls up over wiper C, breaks the circuit of RM at EG2, and opens the loop at EG1. In the register-controller, AR falls back and energizes magnet BM at AR2 so that the B register takes one step and HR falls back to connect up feed over relay AR once more. In the selector, AG released when the loop was opened and completed a circuit for RM which stepped the selector on to the first contacts of the first group. Relay EG now relapses, breaks the circuit of RM and re-closes the loop over AG which completes a self-interrupting circuit for RM. The relay AR in the registercontroller pulls up followed by HR as before and when the selector reaches the last contacts of the first group, EG energizes and causes the B register to move another step. These operations are repeated until the selector reaches the last contacts of the group preceding the desired group. Relay EG re-operates, but in the registercontroller relay GR energizes over A2 (position 1) and B2 (last position). The feed over relay AR is replaced by a loop over JT, DR, the B register steps to its first contacts, the selector steps on to the first contacts of the desired group and EG falls back. As AG does not now re-operate, CG falls back and completes a fresh circuit for RM and also prepares the test circuit at CG1. The selector hunts for an idle outlet and BG, KG fall back when HG switches through. If all the outlets are busy, E pulls up when the selector reaches the last contacts of the group and opens the circuit of RM. Relay FG energizes and locks, and connects battery over BG (lower) and ground from FG3 to the positive and negative wires. This reversal of current operates DR in addition to JT so that busy relay BF, Fig. 1, is operated over DR1 and releases the register as described for the first code selector. The switching relay H at the first code selector falls back since its holding circuit is opened at BF3, and the second group selector releases. Relay group at outgoing end of junctions. This comprises a relay JK, Fig. 4, individual to the junction, and relays JL, JM common to junctions leading to selectors having the same common control relays. Relay JL operates over the test circuit in the preceding selector and cuts out its low resistance winding to busy the junction group. Relay JM is subsequently. operated over a common third wire from the incoming selector and completes a circuit for JK (upper). This relay locks up and releases JL so that other junctions in the group now test busy over JL2, JM1. Incoming selector, Fig. 4. Relay KS operates over the loop in the register to ground on wiper C, locks over FS5 and connects up the common control relays. The operation of this selector is substantially the same as that of the preceding selector except that when DS operates it extends ground over a common third wire to operate the junction relay JM, and further, when the selector is switched through the reverting