Patent GB-270794-A (GB)
Title: Improvements in telephone systems
IPC: H04Q3/42
Filed: 1926-02-10
Abstract: 270,794. Standard Telephones & Cables, Ltd., (Deakin, G., and Polinkowsky, L.). Feb. 10, 1926. Automatic exchange party-line systems.-Reverting calls on a two-party line are established by dialling into a register-controller a particular number (e.g. OO), upon receipt of which the register-controller makes a test over the calling line to determine which is the calling party and thereupon connects up ringing-current to call the other party. In the system shown, calls from a two-party line PA. PB, Fig. 1, are extended over finders 1LF, 2LF to a group selector, Fig. 1<A>, which then seizes an idle register controller, Fig. 2A. The manner in which the registercontroller is modified in order to carry out the present invention is illustrated in Fig. 2. Finders ILF, 2LF. When subscriber PA calls, line relay Lsr energizes over the loop in series with both windings of differential relay Lr, which does not operate. If, on the other hand, subscriber PB calls, the circuit for relav Lsr passes to earth at the substation, and relay Lr, having current through only one winding, pulls up. In either case, relay Lsr energizes the starting relays Fsr, Asr and magnets P of the first line-finders, and when the calling line is found, relay Ltr energizes over wiper d and causes the operation of relays Lhr, Csr, Bsr. Circuits are now completed over cams Q for relays Nmr in all idle second-finder links, and the latter relays energize the power magnets PF. When the calling first-finder link is reached, relav Gtr in the successful second-finder link energizes over cam G and wiper H and opens the driving circuit. Seizure of register-controller. Relay Gtr also completes a circuit over cam H for relay Shr which in turn energizes relay Pgr. Relay Pgr closes a circuit over wipers G, c for relays Ler, Cor in series, releases relay Nmr, and moves sequence switch R into position R in which magnet RC is energized. When an idle registercontroller is reached, relay Gtr is energized over wiper g and cam I (of switch R4, Fig. 2A) and opens the driving circuit. Relays Shr, Pgr now energize as before and switch R moves to position S in which relay Isr operates over wipers a, b and the calling loop and causes switch R4 to move to position 5. Setting of register-controller. The ten impulses of the first digit are repeated by relay Isr over cams U, Q(R4) to the counting-chain Acr, Bcr which they set in a manner similar to that described in Specification 257,307, with the result that at the end of the digit relays Acr5, Acr4.0, complete a circuit of over cam R for relay Spr. At the first release of relay Isr, relay Lmr moves switch R4 to position 6 whilst the relapse of this relay at the end of the digit moves the switch to position 8. The second digit is then similarly recorded on the chain Ccr, Dcr, and at the end of this digit a circuit is completed over cams J, M and contacts of relays Ccr4.0, Dcr6, for relay Por. Control of selectors. In position 6¥ of switch R4, switch R5 moves to position 2 in which relay Osr energizes over wiper d, cam F(R) in series with relay Glr which moves switch R to position 6 and connects up trip-spindle magnet P2. The operation of relay Osr completes a circuit over contacts of relays Bcr5, Bcr6, .. Bcr4.0, Byr, and cam M for relay Scr, so that at the first deenergization of relay Osr, relay Tcr energizes in series with relay Scr and opens the fundamental circuit, and switch R5 moves to position 3. The release of relay Glr causes switch R to move to position 7 in which relay Glr energizes again over cams F, D and the back contact of relav Gtr and connects up the brush magnet P1. When an idle second group selector is found, relay Gtr operates over cam H and brush K releasing relay Glr and magnet PI and driving switch R to position 9. The control of the second group selector, which is set to a special level reserved for reverting calls, then takes place in a similar manner, after which switch R5 moves to position 6¥. Ringing. The operation of relays Spr, Por, referred to in a preceding paragraph, completes a circuit over cam G(R5), V, for relays Rc1r, Rc2r, Fig. 2, which lock up and connect relay Prr over cam X to the b-wire. If party PA is calling, relay Prr does not energize and ringing current is connected over cam X and the b-wire to ring party PB. If, however, party PB is calling, relay Prr energizes over ground on the b-wire at PB's station and ringing current from cam X is connected over the front contact of relay Prr to the a-wire to ring PA. Resistances y, z are so proportioned that the leak of ringing current over the b-wire is small. Relay Rc2r connects up a slow interrupter to relay Lmr causing switch R4 to move step by step into position 16. Release of register-controller. Swith R4 moves to position 18 over cam B, front contact of relay Rc2 and back contact of relay Lmr. In position 14 of switch R4, a circuit is closed over cams T, P, Fig. 2A, for moving switch R5 to position 11 and further circuits to position 18 are closed over cams B(R5) and N, J(R4) and to position 1 over cams C, O. In the first group selector, relay Csr<1> causes switch R to move to position 10, in which it remains during conversation. Metering.-The operation or non-operation of differential relay Lr according as subscriber PB or PA is calling, as described in a previous paragraph, serves to connect up to the third wire one or other of the meters SM2, SM1. Fault alarm. In the modification shown in Fig. 3, the differential relay Lr is connected to a divided battery in the manner shown, so that if an earth exists on either line wire, relay Lr will energize and, after a time interval, an alarm TA will be operated.