Patent GB-141081-A (GB)
Title: Machine switching telephone exchange systems
IPC: H04Q3/42
Filed: 1918-02-25
Abstract: 141,081. Western Electric Co., and Polinkowsky, L., (Western Electric Co.). Feb. 25, 1918. Automatic and semi-automatic exchange systems; metering-systems.-In a system in which a call is extended over a two-wire trunk to a groupselector and thence to a further selector, the closure of the selection-controlling circuit at the controlling-end is prevented until the group-selector has found an idle further selector, and conversely the closure of the selection-controlling circuit at the further selector is prevented until the controlling-apparatus is ready to control further selection. In the system described, calls are extended over connecting-circuits controlled by sequence switches having two talking positions. 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 the call through a first selector D, Fig. 1. The call is then extended in one of several ways according to the nature of the wanted line. Thus, the call may be extended (1) over second and final selectors, Fig. 3, to a local ordinary line, (2) over a two.wire trunk, Fig. 4, to a modified second selector at a distant exchange, this being the principal feature of the invention, (3) over either form of second selector to a toll operator's position, Fig. 5, or a complaint or information desk, Fig. 6, without passing through a final selector, or (4) direct over the top level of the first selector to a distant manual exchange, Fig. 7. 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 Specification 141,080. The switch 220, Fig. 1, 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 registercontrolling sequence switch 320 to move into its third position, wherein the ten-thousands register 100 is connected over contacts 328 top, 330 top, and front contact of relay 326, to the front contact of the impulse relay 325. Operation of register by calling-subscriber. This proceeds substantially in the manner described in Specification 141,080. except that, as the capacity of the exchange is assumed to be 20,000 lines, the controlling-switch 320 has more operative positions than the corresponding switch in the prior Specification, and five registers 100, 110, 120, 130, 140 are used, responsive to the tenthousands, thousands. hundreds, tens, and units digits respectively, in the third, fifth, eighth, tenth, and twelfth positions of the switch 320. Control of first group-selector by registers 100, 110; translation. The capacity of the system is assumed to be 20,000 lines, the group and final selectors being 200-point switches. The selection of the level in the first selector is therefore determined by the setting of the ten-thousands and thousands registers 100, 110. Certain levels of the first selector are reserved for calls over a twowire trunk to a distant exchange, such levels being determined by the first two digits of the wanted number. It will be assumed first that a local call is to be made, and that the ten-thousands digit of the wanted line is unity and the thousands digit even, as for example in calling- line 12453, and that the dial sends numbers of impulses complementary to the digit called. The register 100 has therefore made nine steps under the control of the dial and one step under control of contact 330 bottom, and is therefore again in its normal position O. Register 110 has been energized eight times and is therefore in position 8. When the switch 320 moves into its sixth position after the setting of the registers 100, 110, the switch 350, controlling the successive selecting-operation, moves into its third position. As it passes its second position, a differential relay 359 is energized over its right-hand winding and keeps open the circuit for re-setting the registers. In the third position of switch 350, the fundamental circuit is closed over contact 356 top, armature of cut-off relay 357, stepping-out relay 355, wire 296, contact 247 bottom, Fig. 1, and relay 222, which moves the switch 220, Fig. 1, into its sixth position, wherein the tripping- spindle is set. The energization of relay 355 deenergizes the differential relay 359, thus preparing the circuit for the register 110, the circuit being completed over contacts 112, 361 top, and back contacts of relays 359, 355 each time the relay 355 is short-circuited in the usual manner by the rotation of the tripping-spindle. The register is thus restored, as in the prior Specification 141,080, to its normal position, and on the following de-energization of relay 355, the cut-off relay 357 is energized over its right-hand winding, contact 363 top, contact 104 of register 100 (which is already in its normal position since the first digit of the wanted line is unity), contact 114 of register 110, contacts 364 bottom, 361 top, and back contacts of relays 359, 355 to ground. Relay 357 opens the fundamental circuit, deenergizing relay 222 and moving the switch 220 into its seventh position in which an idle second selector is selected. Switch 350 is energized in parallel with relay 357 and moves into its fourth position, in which it awaits the setting of the hundreds register 120. If the ten-thousands digit of the wanted line is even (e.g. in calling. line 22453 on a distant exchange), the register 100 receives eight impulses from the dial and one over contact 330, and is therefore set in position 9. When the fundamental circuit is closed, the register 110 is reset in the manner described, and when it reaches position 0, the following de-energization of relay 355 energizes register 100 over contacts 114, 102. The register 100 then moves to position 0, so that switch 350 and relay 357 are energized on the next de-energization of relay 355. The trip spindle of the group-selector thus makes an additional step, so as to select an even instead of an odd level. If the thousands digit is odd (e.g. as in calling-line 13453), the first selector is set to the same level as if the next-lower even figure had been dialled, while the second selector is operated to choose a different level, as described later. In the case assumed, the register 110 receives seven impulses and is arrested in position 7, in which contact 116 is closed. As the switch 350 moves through its second position, contact 371 completes the circuit of a relay 360, which locks up and modifies the circuit of register 110 in such a way that this register, when under the control of the stepping-relay 355, is arrested in its ninth position instead of in its tenth or normal position. The tripping-spindle of the first selector is therefore moved to the same position whether numeral 2 or numeral 3 has been dialled. When the switch 350 leaves its third position after the first selector has been set, relay 360 is de-energized, and the register 110 is moved on to its tenth position after the register 120 has been restored, as described later. Selection of idle second selector. This takes place in the seventh position of switch 220 as described in Specification 141,080, and when an idle selector is found, the switch 220 moves into its ninth position, in which the fundamental circuit is extended over contacts 247, 255 to the relay 422, Fig. 3. Control of second selector, Fig. 3, for local call. As soon as the hundreds register 120 has been set, switch 320 moves out of its eighth position, and switch 350 is moved into its sixth position, wherein the fundamental circuit is completed over relay 422, Fig. 3, contacts 404, 247, Fig. 1, wires 296, stepping-out relay 355, armature of cut-off relay 357, contact 356 bottom, back contact of relay 365, wire 297, and contacts 255, 405, to earth. (The relay 377 in the fundamental circuit is short-circuited by the armature of relay 365, which is only energized in certain special circumstances referred to later). Relays 422, 355 are both energized, relay 422 moving the switch 420 into its second position, in which the tripping- spindle rotates, intermittently short-circuiting the fundamental circuit and relay 355, which repeats the impulses to the hundreds register 120 over the armature of relay 359 and contact 366 bottom. If the thousands and hundreds digits are both even, as in calling-line 12453, when the register 120 reaches normal, the relay 357 and switch 350 are energized. Switch 350 is moved into its ninth position, and relay 357 interrupts the fundamental circuit, de-energizing relay 422, which moves switch 420 into its fifth position, wherein the selector brushes rotate to find an idle final selector. When this is found, the relays 434, 432 are energized in known manner, and the switch 420 is moved into its tenth position wherein the fundamental circuit is extended to the final selector. If the thousands digit is odd, as in calling-line 13453, the register 110 has been arrested in its ninth position, as previously described, and after the register 120 has been restored, the circuit is extended to register 110 to move this into its tenth position, whereupon the fundamental circuit is opened and switch 350 moved into its next position. The tripping-spindle of the second selector is thus given an additional step when the thousands digit is odd. If the hundreds digit is