Patent GB-372527-A (GB)
Title: Improvements relating to telephone systems
IPC: H04M5/08
Filed: 1931-04-17
Abstract: 372,527. Manual exchange systems. DONOVAN, W. T. J., 39, Midhurst Avenue, West Croydon, and WOLLEY, G. L., 25, Greenheys Drive, South Woodford, London. April 17, 1931, No. 11389. [Class 40 (iv).] A junction over which calls from one exchange to another are set up manually may be connected automatically in response to the direction or value of signalling current connected up by the calling operator, to an idle one of a number of junctions to one or more further exchanges. The number of exchange selections may be increased by the use of A.C. as an additional signal. In one system, Figs. 1 and 2, two jacks AB(a) and AB(b) are connected to the junction from exchange A to exchange B, the line connections of. AB(b) being reversed. The operator at B is called by using jack AB(a), but if jack AB(b) is used, a line switch W1 .. W4 at B connects the junction to an idle junction to exchange C and the operator at C is signalled. If, however, the calling operator applies A.C. to line, the call is similarly extended to exchange D. Similarly, the operator at B may call exchange C or extend the call to D. Any of the junctions may be used for direct traffic in either direction between two exchanges. In another system, Fig. 3, three exchanges X, Y, Z may be reached from A through B in a similar manner. First system, Figs. 1 and 2 ; calls between adjacent exchanges. In a call from A to B, the operator at A uses jack AB(a) and battery over the ring conductor operates relay B at B to light calling lamp ABcl. The operator at B plugs into ABaj and sleeve relay Z connects the calling line to the jack and disconnects line relays A, B. A call from B to C is made by plugging into jack BC(a) and similar operations ensue but, in addition, relay K at B pulls up to busy the B-C junction in the banks of switch W1 .. W4. A call from C to D proceeds in the same manner as one from B to C. In a call from C to B, the calling operator uses jack CB(a). Battery on the ring conductor operates L at B which lights lamp CBcl, busies the junction to switch W1 .. W4, and busies the jacks BC(a) and (b) by connecting battery to the sleeves. The operator at B responds by plugging into CBaj whereupon M releases L and takes over its busying functions. Call from exchange A to exchange C or D. The operator at A now uses jack AB(b) which has its tip and ring connections reversed so that, at exchange B, relays H, A pull up followed by Y. Relay A falls back but slowto-release relay H is held by Y which locks dependent on H. Switch W1 .. W4 now hunts for an idle junction to exchange C, and when this is found P pulls up in series with magnet DM, switches through, busies the jacks BC(a) and (b), and operates K to mark the junction busy in bank W3. Busy flash BB had been connected up by Y but is rapidly removed if an idle junction is found. At exchange C, relay B pulls up in series with H at exchange B, lights lamp BCcl and busies jack CB(a). When the operator at C responds, Z pulls up, switches through to jack BCaj, and releases B, the busying of jack CB(a) being maintained over the sleeve of jack BCaj. If the call is required to proceed to exchange D, the same operations ensue except that the operator at A momentarily applies A.C. to the line. Relay R at exchange C has been operated in series with B so that X pulls up in response to the A.C., locks up, prepares the reversal of connections to wipers W1, W2 and operates Y, which disconnects jack BCaj. Switch W1 .. W4 hunts for an idle junction to D, P switches through when one is found, lamp L1 lights up, and the C-D junction is busied by relay K. Call from exchange B to exchange D. The calling operator uses jack BC(b) (normal connections reversed), K, Fig. 2, busies the B-C junction and disconnects L which is used in a C-B call. At exchange C, H and A operate in series followed by Y and A falls back, Y being held by H. Switch W1 .. W4 hunts for an idle junction to D and P switches through. Jack CB(a) is busied by relay Y, relay K busies the C-D junction, and jack CD(a) is busied over wiper W4. The call can also be made from jack BC(a), Fig. 2, if the operator at B momentarily applies A.C. to the line (see preceding paragraph). Second system, Fig. 3. Exchange A is connected by a junction to exchange B which has three groups of junctions to exchanges X, Y, Z. Three calling jacks are provided at exchange A, jack AB(a) having normal and jacks AB(x) and (y) reversed connections while jack AB(y) has a resistance in its ring circuit. The rings of A B (x) and (y) are connected at exchange B to relays A and B of which A does not respond to weak current. When both relays operate to strong current contact a operates before b. In a call from A to B, jack AB(a) is used, BL and R pull up in exchange B, calling lamp ABcl lights up and relays A, B are disconnected. When the operator at B plugs into jack ABaj, sleeve relay BR switches through to the jack and releases BL. Calls from exchange B to X, Y, Z are made over jacks BX(a), BY(a), BZ(a) the sleeve relays KX-KZ serving to busy the corresponding junctions in the banks of the hunting switches. In a call from A to X, the operator at A uses jack AB(x) and relays H, A, B at exchange B all pull up. Relays X and Y energize (X before Y) and lock up, the connection of the junction to switch WX1 .. WX4 is prepared, and A, B release. The circuit of magnet DMX is made and that of DMY is disabled while the circuit of DMZ is not affected. Switch WX1 .. WX4 hunts for an idle junction to exchange X and PX switches through when one is found, the junction being marked busy in bank WX3 by relay KX, and jack BX(a) being busied over WX4. Battery over the ring (upper) conductor at exchange A operates XL at exchange X to light the calling lamp. In a call from A to Y, jack AB(y) is used and weak battery over the ring operates H and B but not A. Relay Y pulls up and locks, prepares the connection of the junction to switch WY1 .. WY4, releases B, and completes the circuit of DMY. When an idle junction to Y is found, PY pulls up, completes further points in the speaking connection, and connects a calling battery from r1 over WY1 to operate YL at exchange Y. When the operator at Y responds, battery connected to the ring conductor of her jack operates R at exchange B and F at exchange A. Relay R completes the speaking connection and F short-circuits resistance G. In a call to exchange Z, the operator at A uses normally connected jack AB(a) and relays R, BL at exchange B pull up and complete a circuit for C which responds to A.C. momentarily connected to line by the operator at A. Relay Z pulls up, locks, and completes the driving circuit of DMZ. The call is completed as for a call to X. It will be noticed that the connections of the calling junction to wipers WZ1, WZ2 are reversed as compared with the connections to WX1, WX2 and WY1, WY2. This is necessary since a normally connected jack AB(a) is used for a call to Z.