Patent GB-446917-A (GB)
Title: Improvements relating to telephone systems
IPC: H04Q3/00
Filed: 1934-11-14
Abstract: 446,917. Exchange systems. SIEMENS BROS. & CO., Ltd., Caxton House, Tothill Street, Westminster, and PATTERSON, W. G., 59, Grove Park Road, Mottingham, and DIXON, R. G., 234, Avery Hill Road, Eltham, both in London. Nov. 14,1934, No. 32769. [Class 40 (iv)] In a system in which a calling line is extended to an operator's position by one or more finderswitches, the call being completed manually, upon release by the calling party his line circuit becomes free, but the finder-switches are marked busy and remain in their set positions until the called party hangs up, thus enabling the operator to identify the calling party. As described, calling lines are extended by regular primary finders (Fig. 7) directly to plug-ended connecting circuits (Fig. 15), or by overflow primary finders which lead by way of secondary finders and cord-seekers (Fig. 8) to similar plug-ended circuits or to jack-ended night-service circuits (Fig. 17). The arrangement of finders and allotters, which is described in detail in the Specification, resembles that shown in Specification 422,644, in which the primary allotters are preferentially arranged in relation to the groups of subscribers' lines, each being capable of allotting an appropriate finder, and are such that a regular finder is allotted in preference to an overflow finder, while the secondary allotters are preferentially arranged in relation to the groups of primary finders. Ordinary connection. It is assumed that this extends from the line circuit, Fig. 1, over a primary finder (Fig. 7), a secondary finder and cord-seeker (Fig. 8) to the operator's position (Fig. 15). Line relay LS applies a marking to wire ps and closes the start circuit 2yz, whereupon a primary allotter assigns a primary finder and determines the set of wipers to be used. The primary finder is marked over wire rf from the primary allotter, and the secondary finder and cord-seeker operate simultaneously. The calling loop is extended by switching relays HF, HS to the cord circuit, and line relay LC energizes followed by BC. Relay HS is now held over wire pc, HF is held over wire pf and LS is held in series with cut-off relay KS over wire ps. The primary and seconday finders are marked busy by the removal of battery from wires la, gs respectively. As long as a secondary finder is in use, wire gc is opened by GS or HS. When all the secondary finders of a group are in use, GC, Fig. 9, operates and removes battery from wires la of the primary finders which lead thereto. Relay BC lights the calling lamp AC or CC dependent on BT which operates or not over the metering wire mc according to the class of subscriber. Relays PC, PF energize, extending the call to the operator's set and sending three " pips " to tell the subscriber to state his requirements, the last " pip " being heard by the operator. This is effected by a chain of relays UO-YO which operate and release in turn and a relay ZO which operates intermittently. The cord circuits are formed in two groups with pairs of relays PC, PF and PD, PG individual thereto, the arrangement being such that while a call is being dealt with in one group, a waiting call may be received in the other group. When a whole group of cord circuits is in use, CG, Fig. 9, operates and connects up GC to render the corresponding secondary finders unavailable The operator sets up the wanted call by plugging into the appropriate jack JM without making a test. Contacts ps close to control locking circuits. If the wanted line is idle, relays MC, NC energize in series with the cut-off relay, disconnecting the cord circuit from the position equipment, connecting in the called supervisory lamp CS, earthing the sleeve circuit and connecting up JC. The latter disconnects the calling lamp and PC, so that a waiting call in the other group of cord circuits now becomes visible. Ringing takes place, and upon reply ring-trip and back-bridge relays FC, DC operate. If there is no reply, the calling party initiates release as described below. If the wanted line is busy, MC energizes but not NC, so that busy tone is sent. If the wanted number is unavailable, the operator plugs into a jack from which NU tone is supplied. Release. When the called party hangs up, DC falls back, disconnecting NC, which frees the called line circuit and lights lamp CS. When the calling party subsequently hangs up, LC, BC fall back, lighting lamp CC and disconnecting JC. Earth is thus removed from wire pc to release HS, Fig. 8, which in turn removes earth from wire pf to release HF, Fig. 7, and this relay frees the calling line circuit. Battery is replaced on wires la, gs to render the finders available. Relay MC remains held until the operator takes down, and then replaces battery on wire pc to make the cord circuit available. If the called party holds the connection after the calling party has hung up, relay HA energizes in the position circuit, since LC is back and DC is still up, and lights alarm lamp CL, while wire ch is earthed to operate CH, Fig. 8, which lights lamp CHL, opens wire gs, and connects earth via wire cf to wire la, Fig. 7. When BC, JC fall back, HS, Fig. 8 and HF, Fig. 7, release and free the calling line, but the finders remain unavailable. The operator is able to identify the calling line by noting the positions of the finders. It will be seen that wiper-switching relay DF, Fig. 7, if operated is now locked. Night connection. A key is thrown to prepare a circuit for relay NS, Fig. 8, which is completed by GS when the secondary finder is taken into use, and the cord-seeker hunts over its upper set of wipers which connect to a night-service circuit (Fig. 17). This terminates in a jack JN and the wanted connection is completed over a cord-circuit in the usual manner. The finders are held by earth on wire pn, and the circuit is unavailable until battery is replaced on wire pn when the operator takes down. When the calling party hangs up, earth is connected to wire cn by the relapse of LN to operate CH, Fig. 8, as described above.