Patent GB-214710-A (GB)
Title: Improvements in telephone systems
IPC: H04Q3/42
Filed: 1923-01-23
Abstract: 214,710. Western Electric Co., Ltd., Western Electric Co., Inc.). Jan. 23, 1923. Automatic exchange systems.-A register-controller, of the type which translates the arbitrary designation of the wanted exchange into an appropriate routing number, is arranged to control the selector on the revertive impulse principle. The exchange register consists of a 6-wiper Strowger switch, Fig. 5, which co-operates with a relay counting chain, shown at the top of Fig. 4, to translate a 2-digit exchange designation into a 4-digit routing number. Line switch, Fig. 1, and switch for selecting idle register controller, Fig. 2. The line relay 103 energizes the stepping magnet 105 through the wiper 111 which is grounded at first through its normal contacts and then through grounded terminals of busy trunks. When an idle trunk is reached, the cut-off relay 104 is energized through both windings in series with the left winding of relay 103 over a circuit 111, 118, 203. Relay 104 locks itself through its upper winding over circuit 117 in series with relay 206, which opens circuit 118 and energizes relay 212, which drives the sequence switch 210 to its 2nd position and closes a circuit for the stepping magnet 211. As long as the wiper 241 engages the grounded terminals of busy register-controllers, the relay 212 is kept energized over its left winding and contacts 251, 220. When an idle register-controller is reached relay 212 relapses and a high-resistance relay 207 being no longer shortcircuited becomes energized in series with the magnet 211, which is of too low resistance to respond. The relapse of relay 212 drives switch 210 to its 3rd position. Relay 207 grounds the wiper 241 to energize relay 402, which locks itself and drives the switch 410 to its 3rd position. Operation of registers by dialled digits. The calling line is now extended to relay 400 and coil 401. Relay 400 energizes relay 404 which completes a dialling tone circuit and energizes relay 500 over circuit 425. The first digit is repeated by relay 400 in a circuit 405, 412, 424 to the vertical magnet 504 of the exchange register. A branch of this circuit extends through a back contact of magnet 504 over circuit 422, 413 to relay 406, which grounds the circuit 405, 412, 424 to keep the magnet 504 energized independently of relay 400 until it completes its stroke and opens its back contact to de-energize relay 406, whereby a defectively short impulse is made effective. At the end of the digit the sluggish series relay 405 relapses and unlocks relay 500 (the original circuit of which is now open at contact 531) so that the second digit is repeated to the rotary magnet 503. Relay 405 now closes a circuit 423, 427 for the back-stroke magnet 416, so that at the termination of the digit the auxiliary switch 411 - - 415 is moved to its 2nd position. The remaining four digits are repeated to the magnets 541, 546, &c. to operate the number registers 540, 545, &c., the switch 411 - - 415 being moved a step forward at the end of each digit. Class register, Fig. 4. With the switch 411 - - 415 in its 2nd position, i.e. as soon as the wanted exchange is recorded, relay 407 is energized and locks itself and drives the class register 410 until relay 471 is energized, which occurs in a position determined by the wiper 511 of the exchange register. Thus the switch 410 is stopped in a position appropriate to the class to which the wanted exchange belongs. In the present instance it is assumed that the switch 410 is stopped in its 10th position by the energization of relay 471 in a circuit 472, 476, 511. Relay 471 locks itself and moves the switch 440 to its 2nd position. District selector, Fig. 2. Relays 445 and 212 are now energized in the fundamental circuit 444, 445, 443, 447, 242, 251, 212. Relay 445 energizes an appropriate relay of the counting chain (for example, the relay 450 if the first digit of the translated exchange number is 2) over circuit 469, 512, the bank of the wiper 512 being wired to different points of the counting chain as indicated by the figures in circles. Relay 212 drives the switch 210 to its 4th position, and the updrive magnet 224 is energized. As the shaft 248 rises, the commutator 230 intermittently grounds the fundamental circuit over contacts 220, 251 to short-circuit relay 445, which oscillates its armature and causes the counting chain to build up in known manner, until finally the relays 453, 466 are energized in parallel. Relay 453 drives the switch 440 to its 4th position, unlocking the chain of relays, and relay 466 opens the fundamental circuit to de-energize relay 212, which drives the switch 210 to its 5th position. Magnet 225 is energized to trip a selected set of brushes, and the fundamental circuit is again closed, energizing relay 212 which drives the switch 210 to its 6th position to energize the up-drive magnet again. The control of the second movement of the selector is similar to that of the first, except that the commutator 231 is now active instead of 230, and the contact of relay 445 is connected to the counting chain over wiper 513 of the exchange register instead of wiper 512. The second movement brings the selected brushes to the first of a selected group of lines. The movement is stopped by the de-energization of relay 212 when the relays 453, 466 become energized, and the switches 440, 210 are moved respectively to their 6th and 7th positions. Relay 212 is now energized again over its right winding and contacts 214, 208 and drives the switch 210 to its 8th position. If the first trunk of the group is busy, relay 212 remains energized over its left winding, contact 222, and test brush 235 and again energizes the up-drive magnet. As soon as an idle trunk is found, relay 212 relapses and drives the switch 210 to its 10th position, and the test brush is grounded through contact 222. Office selector, Fig. 3. With the switches 440, 210 in their 6th and 10th positions, relays 445 and 300 are energized in a fundamental circuit which extends metallically over the two sides of the trunk 249, 250. The operation of the office selector and its sequence switch 310 under control of relay 300 is very similar to that of the district selector and switch 210 under control of relay 212, but whereas the two numerical movements of the district selector were controlled by circuits through the wipers 512, 513 of the exchange register, the corresponding movements of the office selector are controlled through wipers 514, 515, the switch 440 standing in its 6th and 8th positions. As soon as an idle trunk is found to the wanted exchange the switch 310 moves to its 7th position, in which relay 300 is energized over contact 301 and drives the switch 310 to its 8th position, the relay 300 remaining locked over the test circuit 327. Release of register-controller. The remaining stages of the connection are set up under control of the number registers 540, 545, &c. and the switch 440 then moves to its 14th position, closing a circuit 448, 244, 214 to energize relay 212, which drives the switch 210 to its 15th position. The talking circuit is now switched through at contacts 246, 247 and the calling line is disconnected from the register-controller at contacts 200, 201 and connected to relay 204, which locks the relay 205. The exchange register is released by a magnet 502, energized over circuit 532, 438, and a circuit 438, 411, 477 is closed for magnet 416, which steps the switch 411 - - 415 to its last position, in which the wiper 414 grounds a circuit 479 to restore the registers 540, 545, &c., whereupon a series normal circuit 558 is closed through wiper 415 to step the switch 411 - - 415 to normal. The switch 440 is driven to normal over circuit 438, 411, 439 and switch 410 is driven to normal over a circuit 411, 442, 408. Release after conversation. The relapse of relay 204 when the calling subscriber disconnects himself unlocks relay 205 which drives the switch 210 to its 18th position, in which the district selector is restored by the down-drive magnet 226. The switch 210 is then driven to normal over a circuit 217, 229, 223. The opening of contact 222 unlocks relay 300 which drives the switch 310 to its 18th position to restore the office selector. Meanwhile the relapse of relay 205 has unlocked relay 104 which closes a circuit for magnet 105 over wiper 107 to restore the line switch. Connection to operator by dialling the single digit 0. When the exchange register is raised to its 10th level, an auxiliary vertical wiper 518 is brought on to a terminal 519, so that when relay 500 relapses at the end of the digit a circuit 518, 519, 426, 405, 412, 424, 561, 503 is closed to rotate the register a single step. The wiper 511 is thus brought on to terminal 521 so that the class register 410 is moved 'to its 14th position, with the result that the register-controller is released and the calling line switched through as soon as the call has been steered to an operator's position.