Patent GB-143277-A (GB)
Title: Machine switching telephone exchange systems
IPC: H04Q3/42
Filed: 1918-05-01
Abstract: 143,277. Western Electric Co., and Polinkowsky, L. May 1, 1918. Automatic exchange systems.-In systems in which a selector is controlled by a sequence or like switch, means is provided to cause the advance of the switch if it remains in certain positions longer than a predetermined time. The invention is particularly applicable to systems in which a series of selectors is controlled in succession over a two-wire trunk line, the sequence switch associated with the selector individual to the trunk being adapted in one position to establish a conductive selection-controlling circuit over which the further selectors are controlled, and to be moved out of this position when the selecting operations are completed. The timing-device is arranged to move the sequence switch out of this first position if the selecting operations of the subsequent selectors are not comp'leted within the predetermined time. The invention is described as applied to a system in which a calling-line is connected through first and second line-finders A, B to a connecting-circuit C which is connected by a searching-switch 280 to an idle register set, Fig. 2, which controls the extension of a call through a first selector, Fig. 1, to a two-wire trunk line and thence over second and third selectors, Fig. 3, and a final selector, Fig. 4, to the wanted line. Connexion may bo made through the first selector with a distant manual board by calling a number of two digits, the first digit being such as to advance the ten-thousands register into position 1 or 0. If the second selector on the incoming end of the two-wire trunk is erroneously brought to a dead level, connexion is obtained with the attendant's circuit shown in Fig. 6. The timing-device consists of a sequence switch 580, Fig. 5, which is rotated step by step by an interrupter 589 so long as the sequence switch 520 of the second selector remains in its sixth position, in which the selecting operations are effected. In the system described, translating-arrangements are used to control the second, third, and final selectors. Connexion of calling-line to idle register. When a subscriber removes his receiver, he is connected by the first and second line-finders A, B, in the manner described in Specification 141,080, to a connecting-circuit C, the sequence switch 220 of which is moved into its fourth position. The calling-line is then extended over the contacts of the searching-switch 280 to an idle register set, Fig. 2, over circuits similar to, but not identical with, those described in the above-mentioned Specification. The switch 220 then moves into its fifth position, in which the calling-line is connected over leads 600, 601 to the impulse relay 325, Fig. 2, controlling the setting of the registers. The seizure of the register set causes the register-controlling sequence switch 320 to move into its third position, wherein the ten-thousands register 100 is connected over contact 328 top, and the armature of differential relay 329 to the front contact of the impulse relay 325. Operation of register by calling-subscriber. This proceeds substantially, but not identically, as described in the said prior Specification, except that, as the capacity of the exchange is assumed to be 100,000 lines, the controlling-switch 320 has more operative positions, and five registers 100, 110, 120, 130, 140, are used responsive to the tenthousands, thousands, hundreds, tens, and units digits respectively, in the third, sixth, eighth, eleventh, and thirteenth positions of the switch 320. Control of first selector by register 100. It will be first assumed that the wanted number is such that the translating-arrangements do not come into operation. These will be described in a later paragraph. As the switch 320 moves through its fourth position after the setting of the register 100, the switch 350 is moved into its third position, in which the fundamental circuit is completed from ground over contact 356 top, stepping-out relay 355, wire 296, and relay 222, which moves the sequence switch 220 into its sixth position, wherein the trip spindle is rotated by magnet 248, producing intermittent short circuits around the stepping-relay 355 in the usual way. These impulses are repeated over contact 343, armature of the differential relay 359, contact 364 top, to the register 100, which is moved forward as described in the above-mentioned Specification. When the register 100 reaches its normal position, the cut-off relay 357 and the sequence switch 350 are energized over contacts 363 bottom, 104, 364 top, and armature of relays 359, 355, to earth. Relay 357 opens the fundamental circuit, causing relay 222 to move the switch 220 into its seventh position, whilst switch 350 moves into its fourth position, in which it awaits the setting of the thousands register 110. Selection of free second selector at distant exchange. In the seventh position of switch 220, the power magnet rotates the brushes to select an idle trunk under control of the test relays 234, 232. When an idle trunk is found, relay 234 energizes relay 232, which moves the switch 220 into its ninth position, in which the fundamental circuit is extended over the brushes 536, 537 to the two-wire trunk. The circuit of the test relays 234, 232 extends over the test brush 252 to a resistance 500, Fig. 3, in parallel with which are connected relays 501, 502, and thence over a normal contact of relay 501 to battery. Relay 502 at its left-hand contact completes a holding-circuit for itself and the left-hand winding of relay 501 independent of the latter relay, which energizes and completes a circuit through its right-hand winding, dependent on a relay 503, which is connected during the release of the connexion, when relay 502 da-energizes, to the lead 536 of the twowire trunk. The object of the relays 501, 502, 503 is to keep the two-wire trunk busy at its outgoing end, during the release of a connexion, until the selector at its incoming end is fully restored, as described later. The lead 529 extends to the distant exchange and is common to several trunks such as 536, 537. Control of second selector. As the switch 320 moves through its seventh position after the setting of the thousands register 110, the switch 350 is moved into its sixth position, and if or when connexion has been made to a free second selector, the fundamental circuit is closed from relay 522, Fig. 3, over contact 504 top, lead 536, contact 255 bottom, Fig. 1, wire 297, back contact of relay 378, contact 358 bottom, armature of cut-off relay 357, stepping-out relay 355, wire 296, contact 247 top, lead 537, both windings of relay 523, Fig. 3, coil 524, and contact 506 bottom, to earth. The stepping-relay 355 is not energized owing to the high resistance of relay 523, which is itself energized and moves sequence switch 520 into its second position, in which the fundamental circuit is completed at the second selector over relay 522 and contact 505 top. The stepping-relay 355 now energizes in series with relay 522, which energizes the clutch magnet 528 to rotate the tripping-spindle. As this rotates, the stepping-relay is intermittently short-circuited and moves the register 110 forward, and when the latter reaches its normal position, the cut-off relay 357 and switch 350 are energized. The switch 350 moves into its seventh position to await the setting of the hundreds register 120, whilst the relay 357 opens the fundamental circuit, causing the relay 522 to move the switch 520 into its third position, in which the brush carriage rotates to find an idle third selector. When a free selector is found, relays 534, 532 are energized in the usual way, relay 532 moving switch 520 into its sixth position, in which relay 532 is connected direct to the test brush 512. Control of third selector. When the selector is taken into use, relay 543 moves the switch 550 into its second position, in which the closure of the fundamental circuit at the register is awaited. As soon as the hundreds register is set, the switch 350 is moved into its ninth position, the fundamental circuit being closed over relay 552, Fig. 3, which moves the switch 550 into its fifth position, in which the trip spindle is set under control of register 120 as before, and the switch 550 then moves into its sixth position. The brush carriage is rotated by clutch magnet 561 until an idle final selector is found, when the relays 564, 562 are energized, the latter relay moving the switch 550 into its ninth position, in which the relay 564 is disconnected from the test brush, which is earthed through the relay 562 in parallel with a resistance 570. Control of final selector. As soon as the tens register 130 is set, the switch 350, Fig. 2, moves into its eleventh position., and if or when a free final selector is found, the fundamental circuit is closed over relay 452, Fig. 4, which moves the switch 450 into its second position, wherein the tripping-spindle is set under control of register 130 as before, and the switch 450 then moves into its third position. If or when the units register 140 has been set, the switch 350 moves into its fourteenth position, thereby again closing the fundamental circuit over relay 452, which moves the switch 450 into its fourth position, wherein the brush carriage is rotated under control of register 140 to select the wanted line. Translating-arrangements. The system of wiring the second selectors is such that alternate levels only are used, each level giving access to a 2000-line group, say 8000-9999. The trip-spindle must thus be moved to the same extent for an even digit as for the next odd digit. This is effected by a contact 116, Fig. 2, on the thousands register 110, which, when the thousands digit is odd, energizes a relay 360, so that the register is restored to position 9 when an odd digit is dialled, and to position 0 when an even digit is dialled. Successive l