Patent GB-141080-A (GB)
Title: Machine switching telephone systems
IPC: H04Q3/42
Filed: 1918-02-06
Abstract: 141,080. Western Electric Co., Polinkowsky, L., Hackley, J. G., and Deakin, G., (Western Electric Co., and Stevens, C. E.). Feb. 6, 1918. Automatic and semi-automatic exchange systems; metering systems.-Relates to systems of the kind in which a calling-line is connected to an idle connecting-circuit and thence to an idle registering-equipment, which is operated by impulses sent in by the calling-subscriber, and controls the extension of the call to the desired line. The claims relate to the following features : (1) the opening of the calling-line for a predetermined time either during the setting or controlling operations of the equipment causes the immediate freeing of the line to call or to be called; (2) if the subscriber does not transmit any selecting-impulses, a signal associated with the equipment is operated, and the connexion may then be set up by an operator; (3) if the subscriber calls a number greater than the capacity of the exchange, he is connected to an operator's position. 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 group-selector D, Fig. 1, and final selector E, Fig. 3, to the wanted line. The system has a capacity of 2000 lines, the necessary " translation " being effected by the registers. It will be convenient to describe first the operation of a normal call, the special features of the invention being described in the later paragraphs. Line-finders. When a subscriber removes his receiver, his line relay 201 puts selectable potential on terminal 210 and energizes the common starting-relays 204, which energize the clutch magnets 211 of idle first line-finders. When the finder A reaches the calling-line, the test relay 214 is energized, and when the brushes are properly centred, relay 212 energizes, thereby (1) cutting- off the clutch magnet 211, (2) putting selectable potential on terminal 230, and (3) energizing the common starting-relays 216, which close the circuits of the relays 222 of idle connecting-circuita having access to the first line-finders. Relays, such as 222, close the circuits of the clutch magnets 221 of the second line-finders B. When the calling-line is reached, a circuit is closed over terminal 230, right-hand winding of relay 234, back contact of metering-preventing relay 224, and contacts 227, 282, to ground. Relay 234 closes a circuit through its left-hand winding, and when the brushes are properly centred, relay 232 is energized, thereby disconnecting the clutch magnet 221, and moving the sequence switch 220 into its fourth position. In the third and later positions, a circuit is closed over contact 236 top for relays 235, 213, 207. If a subscriber calls when there are no free first line-finders in his group, a relay 205 remains de-energized, and a guard lamp 206 lights. In order to reduce the number of second free line-finders rotating simultaneously, the connecting-circuits are arranged in pairs in such a way that, when both cords of a pair are free, one sequence switch 220 is in its first position, and the corresponding switch of the other connecting-circuit is in its eighteenth position. If two second line-finders simultaneously make connexion with the same calling-line, the relays 234, 232 of both finders are energized, and the sequence switches move from their first positions. As each switch passes through its second position, the circuit of the right-hand winding of relay 234 is opened at contact 227, and as the current over its left-hand winding is insufficient to energize it when the two relays are in parallel, the relays 234, 232 de-energize, completing a circuit for the metering-preventing relay 224 over its lefthand winding, contact 254 top, contact of relays 232, contact 229 bottom, and contact 265, to ground. Relay 224 locks up over its left-hand winding and prevents the energization of relays 235, 213, 207. Switch 220 comes to rest in its fourth position, and the apparatus associated with the connecting-circuit is restored in a manner described later. Connexion of calling-line to idle register. In the fourth position of switch 220, the searching- switch 280 is energized over contact 244, back contact of relay 232, and contacts 227, 282. As the switch 280 passes from one position to the next, its contact 282 intermittently earths the right-hand winding of test relay 234, and when an idle register set is reached, the circuit of relay 234 is completed over contacts 246, 283, say, wire 293, contact 368 top, Fig. 2, contact 322 top, and left-hand winding of relay 323, to battery. (The contacts controlled by the sequence switches 320, 350 of the register set are separated by the central dot-and-dash line.) Relay 234 connects up its left-hand winding and relay 232, which opens the circuit of switch 280 and prepares a circuit, (which is completed at contact 282 when switch 280 comes to rest) to move switch 220 into its fifth position, in which the calling-line is connected over contacts 242 and 243, 284 and 285, wires 294, 295, and normal contacts of key 301, to the stepping-relay 325. If the searching- switches of two connecting-circuits simultaneously test the same register set, and the corresponding test relays 234 become energized, the latter are not able to maintain their energization over their low-resistance windings in parallel after the opening of contact 282, and the switches continue to search for a free register. Operation of register by calling-subscriber. The relay 323, Fig. 2, which is energized when the register set is taken into use, locks up over its right-hand winding and moves the sequence switch 320 into its third position, in which relay 326 is energized and completes the circuit of the thousands register 100 over contact 328 top, back contact and right-hand winding of differential relay 329, contact 330 top, and armatures of relays 326, and of the stepping-relay 325, which is energized over the calling-line. The second winding of relay 329 receives current over a coil 331, but as the windings oppose each other the relay is not energized. A relay 337 connected in parallel with the register 100 is also energized and closes an earth connexion in parallel with that over the armature of relay 325. The register 100 moves from position O under control of its local contact 101 into its second position, and as the closure of contact 101 short-circuits the right-hand winding of relay 329, the latter attracts its armature and opens the circuit of the register 100, so that this comes to rest in position 1. The calling-subscriber, hearing the dialling-tone transmitted by the interrupter 333 over the transformer 324, then transmits the sets of selecting-impulses in the usual manner. At the first interruption of the line circuit, relay 325 opens the circuit of the lefthand winding of relay 329, which releases its armature to prepare again the circuit of the register 100. When the line circuit is again closed, the register moves into its next position, causing the energization of relay 329 as before. This process is repeated for each impulse transmitted. The relay 337, energized at each closure of the line circuit, maintains the circuit of the register and relay 329 closed until the register has moved into its next position, thus ensuring proper action of the register in spite of variations of speed of the dials &c. The last line interruption being of relatively longer duration, the relay 325 de-energizes for a time sufficient to energize relay 334, which causes relay 323 to move the switch 320 into its sixth position. As the switch moves through its fourth position, the register 100 is moved an additional step by the momentary closure of contact 330 bottom, the purpose of this being to enable the use in the directory of numbers beginning with the digit 1 so as to avoid numbers beginning with the digit 0. In the fifth position of switch 320, the hundreds register 110 is connected over contact 328 bottom, armature and right-hand winding of relay 329, contact 105 of register 100, and armatures of relays 236, 325, to e.arth. The hundreds register is set in the same way as the thousands register, after which the switch 320 moves to its tenth position, wherein the tens register 130 is set, and then to its thirteenth position, wherein the units register 140 is set, whereupon the switch moves to its sixteenth position. The registers takes up positions complementary to the digit numbers of the wanted line, this being effected by the design of the impulse-sender. Control of group-selector by thousands and hundreds registers; translation. The capacity of the exchange is assumed to be 2000 lines, the group and final selectors being 200-point switches. The selection of the level in the group-selector is therefore determined by the setting of the thousands and hundreds registers. When the switch 320 moves from its sixth into its tenth position after the thousands and hundreds registers have been set, the switch 350 is energized over contact 352 top, contact 103 of register 100, and contact 338 top, and moves into its third position. As the switch 350 moves over its second position, relay 359 is energized over its right-hand winding and contact 354, and at its back contact opens the circuit for resetting the registers. When the switch 350 reaches its third position, the fundamental circuit is closed over contact 356 bottom, armature of relay 357, stepping-relay 355, wire 296, contact 247 bottom, and relay 222, which moves the switch 220 into its sixth position, wherein the trip spindle magnet 248 is energized and rotates the spindle, thereby short-circuiting the fundamental circuit in the usual manner. Assuming first that the thousands digit of the wanted line