Patent GB-346715-A (GB)
Title: Improvements in or relating to signalling arrangements in telephone trunking systems
IPC: H04M5/08
Filed: 1930-01-15
Abstract: 346,715. Automatic and manual exchange systems. STANDARD TELEPHONES & CABLES, Ltd., Columbia House, Aldwych, London.-(Western Electric Co., Inc. ; 195, Broadway, New York, U.S.A.) Jan. 15, 1930, No. 1480. [Class 40 (iv).] Junctions incoming to an operator's position are of different character, for example, ordinary junctions, tandem junctions, junctions associated with a call-announcer at their outgoing ends, and the operator's control circuit is adapted to send back different order signals depending on the character of the junction to which it is connected. The junctions may be distributed over a number of positions in such a manner that junctions of different character appear at each position or that the junctions at any one or more positions may be of the same character. In the system described with reference to the figures arranged as in Fig. 10, Figs. 1 and 2 show incoming call-announcer and ordinary trunks respectively which may be connected over an operator's distributing circuit, Fig. 3, to a control circuit, Figs. 4 and 5. The speaking conductors from Fig. 1 to the control circuit are crossed so that when one or other of the junctions shown, Figs. 1 and 2, becomes connected to the control circuit, relay 408 or 410 in the circuit operates and initiates the transmission of an order signal comprising tone in the case of an ordinary junction and reversal of current flow in the case of a call-announcer junction. In a modified system with Figures grouped as in Fig. 11, a tandem junction, Fig. 6, and a call-announcer junction, Fig. 7, may be connected to the control circuit in addition to the ordinary junction, Fig. 2. The call announcer and tandem junctions have a condenser in one or other of the speaking connections leading to the control circuit, while the ordinary junction is connected thereto over a complete metallic circuit so that one or other or both of relays 809, 810 in the control circuit operate so that different kinds of tone signals are transmitted over ordinary and tandem junctions and the current over a call-announcer junction is reversed. The distributing circuit shown in Fig. 3 comprises three sets of key-operated relays controlling three groups of junctions normally associated with a single position. If the right-hand or central group of relays is operated, one or two groups of junctions are transferred to the operator on the right, while the left-hand group of relays w h i c h would normally be operated cut off the position shown from the next position on the left. Arrangement shown in Fig. 10; control circuit seized by ordinary junction. Relay 202, Fig. 2, operates over the incoming junction 200, 201, followed by 205 (i) which completes a series circuit for 204 (ii), 205 (ii), 206 (ii) in which 206 remains inert. Lamp 208 glows. Assuming that the lefthand group of splitting relays, Fig. 3, is operated, relay 212 operates over a chain circuit including lower contact of 301, lower contacts of relays such as 101, 103, Fig. 1, in the sequence circuit of the group of call-announcer trunks such as 121, 122, lower contact of relay 304, lower contacts of relays in the sequence circuit of another group of junctions (not shown) to battery over 306. Relay 216 operates over a circuit including contacts of relays 218 in the sequence circuit of the group of ordinary junctions and the lower front contact of relay 308. Relay 216 opens the above-mentioned chain circuit so that the control circuit cannot be seized by another junction. If the operator's set has been plugged into jacks 525, 526, relay 506 is operated, so that relay 403 is energized in a circuit including the contact of 506 and extending to ground at a contact of splitting-relay 314. Relay 406 pulls up to complete the connection of the junction to the control circuit, and battery over the supervisory relay 222 operates 410, relay 222 remaining inert. It will be seen that relay 408 connected to the other leg of the operator's trunk does not operate. Relay 410 operates 514 which completes a circuit over contacts of 419, 417 for the primary of tone transformer 528, and connects the secondary to the trunk so that tone is transmitted back over the junction, operation of the supervisory relay being presented by blocking condenser 519. Slowto-operate relay 417 opens the primary circuit and closes a circuit for slow-to-operate relay 421 which reconnects the primary and closes the circuit of a further slow-to-operate relay 419 which finally disconnects the tone circuit and operates relay 520 which switches through to the operator and holds 419. When the junction first became associated with the control circuit, relay 428 was operated so that 535 operated by 510 now completes a circuit for 512 which operates 509. At the same time, 436 was operated followed by 437, 438 in turn Relay 438 shunts relay 436 and the lamp 208, and the relapse of 436 releases 437,438, so that lamp 208. flashes periodically until the operator, after attending to the connection, presses key 439<1> to disconnect her control circuit from the junction. Control circuit seized by " call - announcer " junction, Fig. 1. Circuit changes occur as described in the preceding paragraph until the operation of relay 406 when, owing to the crossing of the legs of the trunk from Fig. 1 to the control circuit, 408 pulls up instead of 410 and energizes 524 which cuts condenser 519 out of the secondary circuit of tone transformer 528 and operates relay 435 to start the relay chain 436, 437, 438. Both windings of 440 are connected to conductor 441 and thence to battery over lamp 114 so that intermittent operation of 438 flashes the lamp but 440 remains inert. Relays 443 and 444 operate in turn and complete a circuit for 514 which connects up tone transformer 528 but, as condenser 519 is cut out, direct current over the secondary operates supervisory relay 105 so that 120 pulls up and reverses the current flow over the junction. The superposition of tone over the secondary is without effect since there is no distant operator and the only effective result of the previously described operation of relays 417, 421, 419 is to energize 520 which completes the connection to the operator. Modified signalling with Figures arranged as in Fig. 11 ; ordinary junction, Fig. 2. Relays 204, 205, 212, 216 in the junction circuit and relays 803, 806, 906 in the control circuit (corresponding to relays 403, 406, 506 in Figs. 4 and 5) energize as previously described. Ground and battery on conductors 220, 223 operate 809, 810 respectively and supervisory relay 222 remains inert. Relay 815 pulls up and operates 914 which connects up tone transformer 916, the primary of which includes interrupter 817, and relays 818, 823, 822 operate in turn to give two applications of tone and operate switching relay 918 as described in connection with similar relays in Figs. 4 and 5. Lamp flashing relays 838, 839, 840 also operate as previously described. Tandem junction, Fig. 6. The junction circuit is the same as that shown in Fig. 2 except that a condenser 600 is inserted in one of the legs of the trunk to the control circuit. Therefore, relay 809 responds alone when the control circuit is connected up, energizes 819, and completes circuits for the tone transformer in which low-tone interrupter 842 is connected to the primary. Relay 818 operates as before but, since 819 is energized, the circuit for operating 823 is transferred to 846 which after an interval operates 843 and closes the circuit of slow-tooperate relay 847, so that high - tone interrupter is connected up for an interval in place of 842. When 847 operates, 843 falls back to switch in the low-tone interrupter and a circuit is completed for 823 which, after an interval, closes the circuit of 822 which disconnects the primary of the tone transformer. A signal comprising low - high - low tone is thus transmitted. The remaining operations are as previously described. Call announcer junction, Fig. 7. Relay 810 responds instead of 809 since the circuit of 809 is blocked by condenser 700. Relays 815, 850 pull up in turn, 927, 837 operate to start the lamp-flashing relays 838, 839, 840, and relay 850 connects ground from a contact of 822 to the lower leg of the trunk to operate supervisory relay 703 which reverses the current flow over the junction as previously described. Relay 837 also operates 853, 855 in turn and the latter operates 818 so that 823, 822 pull up in turn. Relay 822 removes the operating ground for the supervisory relay and operates switching relay 918.