Patent GB-201713-A (GB)
Title: Improvements in telephone exchange systems
IPC: H04Q3/42
Filed: 1922-06-23
Abstract: 201,713. Western Electric Co., Ltd., (Western Electric Co., Inc.). June 23, 1922. Semi-automatic exchange systems.- In a system employing both power-driven and step-by-step switches, sending-apparatus normally controlling power-driven switches is modified for the control of step-by-step switches by means of a class register set according to the first digit of the wanted number. The number of impulses in each train is one greater than the actual digit set up on the corresponding register, and revertive impulses are sent back to a chain of counting relays which operate in turn until the last opens the fundamental circuit. The registers are of the sequence switch type, and are set by an operator's keyboard, provision being made for non-decimal translation. Setting of the registers. When the operator plugs into the calling line, a relay 112 energizes, moving the sequence switch 100 into the 2nd position, in which a relay 314 operates to move the sequence switch 300 into the 2nd position. The operator depresses the keys K<1> - - K<5> corresponding to the wanted number, connecting up in parallel the regisber magnets 410, 420, 430, 440, 450, which operate until relays 471 - - 475 become energized over the switch contacts, such as 411. Relays 477, 480 are connected up in series, and the latter moves the sequence switch 300 into the third position, in which release magnets 482 - - 486 are energized, releasing the keys and the relays 471 - - 475, 477, 480, the relapse of the relay 477 moving the sequence switch 300 into the 4th position. Control of power-driven selectors. The fundamental circuit is now established through relays 115, 316 over back contacts of a relay 315 and the counting relay O<1>. The relay 115 energizes and moves the sequence switch 100 in the third position, in which the up-drive magnet 119 is energized to raise the wiper carriage 122, the fundamental circuit being intermittently 'broken at the commutator 124. The first digit being 9, say, the initial operation of the relay 316 connects earth to a wire 353 over the office register cam 412, energizing the counting relay 9, and upon the first de-energization of the relay 316, the counting relay 9<1> operates on the removal of a shunt therefrom, energizing the relay 8. The counting relays 8<1>-0<1> are thus energized in turn, the fundamental circuit being broken by the energization of the relay 0<1>, which also moves the sequence switch 300 into the 6th position, in which the counting relays are released. The relapse of the relay 115 releases the up-drive magnet 119 and moves the sequence switch 100 into the 6th position. Hunting for an idle trunk now takes place. The test relay 125 energizes, moving the sequence switch 100 into the 7th position in which the up-drive magnet 119 is again connected up until the release of the test relay upon connection to an idle trunk. The sequence switch 100 is moved into the 11th position in which the wires 117, 118 are connected to the trunk, and the relay 316 is energized in series with the control relay at the selector 200 in the selected office X over the office register cam 414. Impulses are sent according to the setting of the thousands register cam 421, and the sequence switch 300 is then moved into the 8th position, in which the selector 200 is controlled by the thousands register cam 422 and the hundreds register cams 432. In the 10th position of the sequence switch 300, the selector 200 hunts for an idle connector 201, which moves according to the last three digits set on the registers in the 10th, 12th, 14th positions. The movement of the sequence switch 300 into the 16th position drives the sequence switch 10 into the 11th or talking position, and completes the connection. The relay 314 releases and restores the sequence switch 300 to the normal position. When the operator withdraws the plug upon release, the relapse of the relay 112 moves the sequence switch 100 into the 18th position, in which the downdrive magnet 132 operates to restore theapparatus to normal. Control of step-by-step selectors. The first digit being 3, say, the wiper carriage 122 is raised as before, and upon energization of the counting relay 0<1>, the sequence switch 300 is moved into the 8th position by means of the office register cam 415, thus eliminating one selective position, which is necessary for translation in the control of power-driven switches. Hunting for an idle trunk to the office 7 takes place in the 7th position of the sequence switch 100, which then moves into the 11th position and a fundamental circuit is established for the line relay 251 of the selector 250 and the stepping relay 316 over office register cams 414, 418 and a back contact of the relay 315, the circuit of which includes an interrupter 487. The relay 316 upon energizing connects up the counting relay selected by the thousands cams 423, and the counting relays energize in succession as impulses are sent until the circuit of the relay 315 is broken by the operation of the counting relay 0<1>, which also energizes a slow relav 320 to drive the sequence switch 300 into the 10th position, thus allowing sufficient time for the selector 250 to perform its hunting movement. The second selector 256 is operated in a similar manner, and the connector 257 responds to the last two digits. Completion of the connection and release take place as before.