Patent GB-459792-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04M3/60
Filed: 1935-07-11
Abstract: 459,792. Exchange systems. AUTOMATIC ELECTRIC CO., Ltd., Strowger Works, BEALE, C. E., 59, Towers Road, Wavertree, and RICHARDS, I. T., 50, Meadway, Wavertree, both in Liverpool. July 11, 1935, No. 19854. [Class 40 (iv)] In a system in which long distance calls are set up over cord circuits, an amplifier is automatically inserted in the connection when the operator throws a gain key in the cord circuit. The amplifiers are common to a number of positions and are associated with the cord circuits by means of finder switches. The direction of operation of the gain key controls the gain of the amplifier. General arrangement. Two-way trunks may be connected at a frame 1DF, Fig. 5, as desired to the trunk selector banks, and to jacks at special positions SLP, incoming positions ICP, revertive positions RVP and long distance positions LDP. When the distant operator rings, relays L, LL pull up, guarding the trunk and lighting calling lamps CL at the incoming positions and engaged lamps VES at all the positions. An incoming operator inserts answering plug AP, Fig. 6, and throws speak key KS, whereupon relays SK, SL operate. The position equipment (not shown) is similar to that described in Specification 459,803. Relay CS energizes over the sleeve circuit in series with AS and connects up SS, BR, which extinguish the calling lamps. If the call is for a local subscriber, the operator inserts calling plug CP in a jack leading to a first code selector and keys the number as described in Specification 459,803. The completed connection is under the control of the distant operator, and she may recall the incoming operator by ringing, whereupon relay Z responds and intermittently short-circuits CS, thereby flashing lamp ANS through the medium of AS. Relay Z is disconnected by R by operation of a key which connects booster battery to the sleeve circuit. The calling party may be re-rung by means of key KRA which controls relay RR. If the call is a through call, the operator plugs into the jack of an outgoing trunk and throws key KRC which controls a ringing relay similar to RR. If all the trunks of the required group are busy, the operator may plug into a jack leading to a trunk selector which camps on the busy group and signals the operator when a trunk becomes idle, as described in Specification 444,256. To transfer a call to a revertive position, the operator throws a key which controls relay TR, whereupon the calling lamps on the revertive positions are flashed while those on the incoming positions are disconnected. Incoming long distance calls appear on the long distance positions only. Insertion of amplifiers. The incoming or long distance operator throws a gain key in the cord circuit to the high position KGH or low position KGL, earth being extended over wire G in the former case to increase the amplification. In either case the cord circuit is marked in the finder banks and one of relays SA-SE, Fig. 8, each associated with two levels, operates and connects up start relay ST, Fig. 13, of a control circuit. As described in Specification 429,767, three control circuits are provided to deal primarily with calls from three sub groups of levels. An idle finder is preallotted by an allotter associated with the control circuit and comprising a pair of switches PA, AA, Figs. 9-11. Relay LK, Fig. 13, energizes to battery over wiper PA1 and connects up VR, these relays being arranged as described in Specification 435,411 to prevent seizure of a finder from two control circuits. Relay PA, Fig. 14, energizes at once or when the switches PA, AA are brought into alignment and connects up HA, B in the finder. Relay LK falls back and connects up DV, which disconnects PA and completes the vertical hunting circuit of the finder. When the marked level is reached, relay LK energizes over wiper PA2 and connects up RS, RX, whereupon change-over relay HB operates. Relays LK, DV fall back, and the rotary magnet operates until wiper P1 or P2 picks up battery over the gain key. Relay PA or PB responds in series with K in the cord circuit, and connects up CO which brings about the release of control circuit. Relay K remains held in series with HA or HB, and switching relay HC or HD operates to connect in the amplifier. Relay K lights lamp RGL, Fig. 7, and the operator restores speak key KS, whereupon KA pulls up and completes the connection through the amplifier. If a control circuit is held for an excessive time, the start signal is extended to another control circuit to give the operator a further opportunity of obtaining an amplifier. If the finder fails to pick up the vertical marking, it restores and a second finder is started up. Routine test keys such as KRT, Fig. 8, are arranged to simulate calls on the various levels of the finders. Precision amplifiers are available at long distance positions and are inserted in the trunks by means of double plugs and jacks, relay KO, Fig. 5, operating in the sleeve circuit to disconnect the ordinary multiple.