Patent GB-263514-A (GB)
Title: Improvements in automatic and semi-automatic telephone systems
IPC: H04Q3/00
Filed: 1925-09-04
Abstract: 263,514. Siemens Bros. & Co., Ltd., and Patterson, W. G. Sept. 4, 1925. Automatic and semi-automatic exchange systems; metering. - Numerical impulses are transmitted between selectors in the same office over a fourth wire. Ringing current is supplied by the first or incoming selector in response to a signal sent back from the connector over this wire. If the subscriber is busy a signal is sent over this wire to the first selector to control the transmission of busy tone and flash, or, if the wanted party is in another office to the incoming selector which sends back busy tone and controls the repetition of a signal over the two-wire trunks involved back to the first selectors which if an operators' selector supplies busy flash. Intermediate selectors have only two relays and connectors four or five and there are no relay contacts in the talking circuit except in the first and incoming selectors. Line switch, Fig. I. This resembles that described in Specification 248,899. Line relay R completes locking, driving, and test circuits and when an idle line is found, relay T switches through, unlocks relay R and holds on to ground returned from the first selector. First selector, Fig. 2. When the loop is switched through, impulse relay A, release relay V, relay DC, and dialling relay D pull up and dialling tone is sent from DS. The first digit is repeated to magnet VM. At the first step, springs k<1> - - k<3> change over to change the circuit of the dialling relay and energize relay L which locks up. At the end of the digit relay D falls back and makes a self-interrupting rotary circuit rm, b2, d2, t5. When an idle line is found, relay T pulls up to battery in the intermediate selector over its winding 1 locks itself over its winding 2 grounds the c-wiper and connects the fourth wiper D1 over the impulse contact a4 to relay DC which now holds in series with the impulse relay of the selector ahead. Intermediate selector Fig. 3. Relay A energizes relay T and repeats the digit to magnet VM. Springs k change over and relay T which short circuits its winding 2 holds up during impulsing over k3 a2 (back). At the end of the digit relay T makes the rotary circuit rm, a3, t5. When an idle line is found relay T pulls up to battery ahead, switches the d-wire through, grounds the c-wiper and, springs w having changed over, locks itself up and releases relay A. Line-relay connector Fig. 4. Relay N pulls up and locks itself when the switch is seized and' relay A energizes relay D and repeats the tens digit to magnet VM. Springs k1 - - k3 change over and at the end of the digit relay D falls back and energizes relay G which re-energizes relay D and prepares the rotary circuit. The change over of rotary springs w1, w2 arranges. for the successive relapse of relays D, G at the end of the units digit. In the interval between the relapse of these relays, relay T tests the line. If it is idle relay T locks up over its low resistance winding to mark the line busy and grounds the d-wire to initiate ringing. If it is busy the relapse of relay G leaves the d-wire dead. Four-relay connector, Fig. 5. Relay N is omitted and the test relay T which is given control of the release magnet for successful calls locks itself to the incoming test wire and grounds the c-wiper direct. The sequence of operations is the same as in the five-relay connector except that in the case of an unsuccessful call, relay A remains held after the relapse of relay G over g4, w1, t1 to prevent the operation of the release magnet. Rotary connector. Either of the above connectors may be adapted for the selection of lines to a private branch exchange by the provision of an extra relay and wiper. Ringing current. The ground on the d-wire short circuits relay DC which after an interval energizes relays WC, R over the d-wire. Relay DC is re-energized over wc5 before relay L has time to fall but relays WC, R remain locked up. Ringing current is sent out over TR (1) and ringing signal is sent back from RS. When the called party replies, relay TR locks up over its winding 2 and short-circuits relay R which cuts off the ringing current and signal and completes the called loop back to the feed relay B which pulls up together with relay Y and short circuits relay H. In case the ringing current is to be provided by the connector, the d-wire is grounded over a resistance which allows relav WC to switch through but prevents the operation of ringing relay R. Busy signalling arrangements in full automatic local calls. If the line switch is unsuccessful or if. while the subscriber is still calling, the test wire of the seized selector is opened, manually or otherwise, the line switch is stepped to congestion terminals associated with a dialling-tone transformer DS. Relay T which is no longer short circuited by wiper D cuts off relav R and locks itself over the loop. When the subscriber dials in response to the signal, relay T is unlocked, the wipers are moved to the next terminals and relay R pulls up again and causes a further step to the terminals associated with the busy transformer BB. Relay T pulls up again to stop the switch but relay R is held over the busy terminals and the loop. When the subscriber hangs up, the switch receives a further step. If the first selector, Fig. 2. is unsuccessful, 11th terminal springs S1, S2 change over. Relay T pulls up and relay DC falls back releasing relay L which removes a short current from TR (2) to allow relay TR to pull up and send back busy tone from BB. If the intermediate selector is unsuccessful, the d-wire is broken by 11th terminal springs S<1> (relay T pulling up over S2. Similarly if the wanted party is busy the d-wire is broken by the relapse of relay G (Figs. 4, 5) and non-energization of relay T. In either case, relay DC, Fig. 2 falls back to initiate the busy signal. Means for repeating a busy signal between offices and for giving busy flash to an operator are described under " Inter-exchange working " and " Operator's first selector," below. Release. The release of relays A, V, Fig. 2. by the calling party is followed by that of relay T and of relay WC which disconnects the talking wipers, removes holding ground from the c-wiper. and energizes release magnet MM. In the intermediate selector relay T falls back and energizes its release magnet. In the connector relay N (Fig. 4) or relay A (or T) (Fig. 5) falls back and energizes the release magnet. During restoration the incoming test wire is held open at k1. Metering and supervision. The answering relay Y releases relay DC which, after an interval closes the metering circuit l3, y1, dc3 and releases relay L which opens it. In the case of calls to a manual board (e.g. as shown in Fig. 3 of Specification 257,685), relay B pulls up when the link is seized but relav Y remains back and relays DC, L are held up and hold the metering circuit open. When the calling party hangs up, relay B is released at a3, relay Y is short-circuited and relay H is allowed to pull up completing an alternative circuit for release relav V over h1, y1, l3. A similar provision is made in the incoming selector, Fig. 6 (described below) which also holds the preceding switches over RC, h2, y3. Exchange attendants' supervisory arrangements; statistical metering. In the first selector, Fig. 2, the lamp CSH is lit by the release relay V when the selector is seized and extinguished by relay L when dialling begins. The lamp glows again if relay L is released as the result of an unsuccessful hunt, and on the relapse of relay Y if the called party hangs up first after conversation. If the lamp is lit for a prolonged period as when the switch is held by a faulty line, a delayed alarm notifies an attendant who operates key K to release it and cause the line switch to move to congestion terminals and send back dialling tone. If the key remains thrown, the selector is marked permanently busy. Congestion meters are operated by the 11th terminal springs in the group selectors. Operator's first selector. Fig. 7, in local calls. The selector is similar to that shown in Fig. 2 but (1) the impulse relay A is controlled over the b wire alone (2) the vertical circuit is held open by an additional relay Q controlled over the a-wire until the dial springs are off-normal, (3) A relay LF energized by relay L when dialling begins connects itself to the a-wire in place of the supervisory relay Y. If the wanted party is idle, the relay LF is released by relay WC, and subsequently when the called party replies, relay Y connects battery over A instead of ground over Q to the a-wire to extinguish the supervisory lamp and also energizes a relay which locks up. If the line is busy, relay WC remains back and relay TR connects busy tone and flash from BB to the outgoing a-wire, the flash signal being repeated to the operator by relay Y. Inter-exchange working. The d-terminals of inter-office trunks are permanently connected to ground over a resistance which allows relay WC to pull up, but not relay R. In this case, relay LF remains locked to the a-wire which is grounded at the selector ahead. The incoming selector resembles the first selector, Fig. 2, but the line relay is controlled over the b-wire alone, a-wire being used for answering and busy signalling and a relay LF similar to that in the operator's selector, is provided. The selector gives access to local selectors and to two-wire trunks in the same way as the selectors shown in Figs. 2, 7. If the wanted line is idle, the relay WC in the incoming selector at the final office releases relay LF to re-instate the relays Y, H, but ground is still connected to the incoming a-wire over tr4 y3. When the answering relay Y pulls up however this ground is replaced by battery which short-circuits the relay LF and energizes the relay Y of the incoming or operator's selector at the preceding office. This selector repeats the signal in the same wa