Patent GB-652602-A (GB)
Title: Improvements in telephone systems with party lines
IPC: H04Q3/58
Filed: 1945-10-23
Abstract: 652,602. Party line systems. COMPAGNIE GENERALE D'ELECTRICITE. Oct. 23, 1945, No. 27964. Convention date, July 1, 1942. [Class 40 (iv)] In a party line substation the exchange is called by the operation of a mechanically locking relay by magneto current (or by the use of a mechanically-locking push-button), which is released by another relay when connection with an operator's circuit at the exchange is effected. Subscriber calls operator. The caller operates his magneto, and operates relay 2, Fig. 1, which removes the short-circuit from the buzzer which is heard by the caller if he lifts his hand set. Relay 2, which then remains operated until released mechanically by the operation of 2x, operates 32 at the manual exchange, Fig. 2, over the B wire, which locks, lights the calling lamp, and causes the sequence switch X3 to move to position 1. The circuit of the busy lamp is thus opened and relays 28 and 29, operated first over contact 323, and subsequently over X1d, interact to energize intermittently the selector switch magnet 1 at the substation and also switch X1 in the exchange circuit. (Magnet 1 is energized first over the A wire and then over the B wire.) The ringing generator is started by a1 and waiting tone sent by contact 326. Each substation of the party line has its contact 31x connected to a different position on the a bank of its selector, and when all the selectors including X1 have been stepped to a position corresponding to the calling station, 26 operates over the B wire, locks, breaks the circuit for 28, 29, and operates 24, which locks. Relay 26 operates relays 2x and 3<SP>x</SP> in series over the B wire and the subscriber's hand set is connected to the A and B wires, and the waiting tone is received. Relay 2x releases 2 mechanically. Relay 22 operates and locks when the operator plugs in, and disconnects the calling lamp ; X3 moves to position 2, whereupon 32 falls but 3<SP>x</SP> and 2<SP>x</SP> are maintained over c2. If the subscriber has hung up he receives ringing current, and when the subscriber takes down his receiver 27 operates, X3 goes to 3 and communication with the operator is established. Relay 3<SP>x</SP> releases, but 2<SP>x</SP> remains held until mechanically released by 3. Relay 24 releases, followed by 31. Relay 23 operates and the supervisory relay 25 operates over the B wire, and lights the supervisory lamp continuously. Revertive call. Operation of the operator's dial key loops wires 1 and 3, whereupon X3 goes to 4 and relay 26 falls, re-establishing the circuits of 28 and 29, which interact to home X1 and all the subscribers' selectors. Register switch X2 also goes home if not already there, after which X3 goes to 5 and 31<SP>1</SP> operates, removing battery from wire 2, so illuminating the operator's dial lamp. Relay 31<SP>1</SP> connects the dial contacts to the impulse relay 21 which steps the register switch X2 in accordance with the wanted subscriber's number. When X1 has homed, relays 28 and 29 are operated first over bank b of X2 and then bank d of X1 to step X1 and the subscribers' selectors until they reach the position corresponding to that of X2, when 26 operates over banks a of X1 and X2, locks and cuts the circuit for 28, 29. When the operator restores the dial key 31<SP>1</SP> and 2<SP>x</SP> fall. Operation of the operator's ring key operates 24 over the tip and ring of the plug, X3 goes to 6 and relays 2x, 3<SP>x</SP> of the called subscriber operate to connect the telephone set to the wires A, B and ringing current is sent over a contact of 31 which operates intermittently, controlled by a cam D2. The supervisory lamp flashes, its circuit having been transferred to the control of a rapid cam D1 by 24. When the called subscriber answers, 27 operates and X3 goes to 7 and 24 falls. Relay 23 operates and connects supervisory relay 25 to line. When the operator withdraws the plug, 22 releases, X3 goes to 8 and conversation ensues. When one subscriber hangs up, 25 operates, and X3 goes to 9, and 23, 25 and 26 then fall, the last causing 28, 29 to send X1 and all the subscribers' selectors home. X2 goes home over c9. X3 goes to 10, and sends battery over wire B to operate relay 3 which releases 2x mechanically. Relay 23 operates and X3 goes to position 0. Outgoing call. This will be established by the operator when X3 is at 3. On completion, 22 falls when the operator withdraws the plug and X3 goes straight to 8, whereupon 23 is re-excited and the apparatus restores to normal as above when the subscriber hangs up. Incoming call. The operator ensures by means of key and lamp L1 that the line is not in use, and then plugs in and operates the dial key. Relay 31<SP>1</SP> operates over the loop placed on wires 1 and 3 by the dial key and suppresses the battery on wire 2, thereby permitting the lighting of the dial lamp. Relay 31<SP>1</SP> operates 22 and X3 goes to 1. Relay 21 repeats the impulses to X2 and X1 and the subscriber's selectors are stepped to the required number as before whereupon 26 operates to interrupt the stepping and operates 24, which locks. X3 goes to 2, 31<SP>1</SP> falls and the dial lamp is extinguished. Negative battery over the B wire operates 2<SP>x</SP> and 3<SP>x</SP> in the substation equipment and ringing current is sent over the intermittently-operated contact of 31, the operator hearing the outgoing ringing current over contact 244, condenser and contact 243. On reply, 27 operates, X3 goes to 3 and conversation takes place. Release takes place as in the outgoing call described above. In a modification, Fig. 4 (not shown), the relay 2 and magneto at the substation are replaced by a mechanically-locking push-button which is released by the operation of relay 2x. In the following description the party line is connected to the exchange via a rural switching centre, Fig. 3, instead of directly as described above. Subscriber calls operator. Operation of 2 by the magneto operates 30, Fig. 3, which locks and puts negative calling battery on wire A<SP>1</SP> to the exchange. The negative pole of an auxiliary battery is connected to earth by a0 and X1d home contacts. When the call has been allotted to an operator at the exchange it sends back negative battery on the B<SP>1</SP> wire which causes polarized relay 1 to operate its - contacts. Relay 26 operates, causing sequence switch X3 to go to 1 and 29 to operate. c1 now connects the positive pole of the auxiliary battery to earth. X1 steps by the interaction of 29 and 27, whose circuit is first completed by contact 262 and subsequently by X1c. The subscriber's selectors also step in response to impulses, the first impulse being over the A wire and the remainder being loop impulses. When the selectors reach the position corresponding to the calling subscriber, relay 28 is operated by the auxiliary battery over its upper coil and wire B, and locks over its lower coil. 28 breaks the circuit for 29 and 27, switches through the speaking conductors, and releases 30, which removes the negative battery from wire A<SP>1</SP> to the exchange and operates relays 2<SP>x</SP>, 3<SP>x</SP> at the calling substation, thereby completing the speech circuit so that the caller may receive the waiting signal from the exchange. When the exchange operator answers, positive battery received on the B<SP>1</SP> wire causes relay 1 to operate its + contacts. X3 moves to 2, maintaining 2x, 3<SP>x</SP> operated at d2 and the talking loop is made wholly metallic at a2. The subscriber receives ringing current from the exchange if he has hung up, and when he replies negative battery from d2 over the subscriber's loop back to the rural exchange operates the ring trip relay there. The exchange then sends out negative battery on. the B<SP>1</SP> wire and positive battery on the A<SP>1</SP> wire. Relay 1 goes to its - position and X3 goes to 3. Relay 3<SP>x</SP> releases but 2x remains held mechanically. Relay 25 operates, connects supervisory relay 23 to the subscriber's line wires and connects polarized relay 1 to the exchange A<SP>1</SP> wire. If the subscriber replaces his instrument supervisory relay 23 operates and opens the loop (through relay 1) to the rural exchange, thereby lighting the supervisory lamp. Revertive call. When the dial key is operated the exchange sends positive battery over the B<SP>1</SP> wire and 1 goes to its + position. X3 goes to 4 and 25 and 28 fall. Negative battery sent over the A<SP>1</SP> wire prevents the operator's dial lamp from lighting. X2 homes first under control of earth over bank X1d, then over e4 and home contact of X1b, which is 90 degrees displaced from the home contacts of X1 a, c, d ; and finally over bank X1b. Relays 27, 29 home X1 and the subscribers' selectors, and X3 goes to 5, operating 22, which removes battery from the A<SP>1</SP> wire to the exchange, which causes the operator's dial lamp to light. Relay 21 repeats dialled impulses received over wire A<SP>1</SP> to X2 which registers the digit. At the end of the impulse train 21 drops, followed by 22. When X1 reaches home, relays 27, 29 are re-operated first over X2c and then X1c to step X1 and the subscribers' selectors until the position of X1 corresponds with that of X2. Relay 28 interrupts the circuit of 27, 29 and the selectors stop. X3 goes to 6. Operation of the call key at the exchange maintains + battery on the B<SP>1</SP> wire and sends ringing current over wire A<SP>1</SP>. When the subscriber answers, negative battery from d6 round the loop operates the ring trip relay at the exchange, which thereupon puts negative battery on B<SP>1</SP>; relay 1. closes its - contacts, X3 goes to 7 and 25 operates, connecting up the supervisory relay 23. The operator withdraws her plug and 1 releases, followed by 26, and X3 goes to 8, in which 25 is held, so keeping supervisory relay 23 on the line during the conversa. tion. An operator endeavouring to call on this line by putting positi