Patent GB-141711-A (GB)
Abstract: 141,711. Turcat, L. April 10, 1919, [Convention date]. Automatic exchange systems; impulse-transmitters.-The impulse-transmitter is set to the desired number and is returned to normal position by a magnet energized by impulses sent from the exchange over one line with an earth return; each time the magnet is energized an impulse is sent over the other line to energize the stepping-magnet of the selector. Construction of impulse-transmitter. A drum 2, Fig. 4, which is turned by a knob 4 until the name or number of the wanted line shows through an aperture in the casing, carries a metal ring 7, which is engaged by a spring 10, mounted together with springs 14, 15 on the face of a ratchetwheel 12 actuated by a magnet 33. The ring 7 has an insulating-stud 11 which comes under the spring 10 so as to open the selecting-circuit when the desired number of impulses has been sent. Similarly, a ring 16, engaged by the spring 14, has an insulating stud 20, Fig. 1, which opens the restoring-circuit after the apparatus has been returned to normal at the end of a conversation. The drum 2 is locked in its set position by an extension 22 on the switch-hook when the receiver is removed. Circuit arrangements. Each subscriber has at the exchange two relays 62, 77 and a selector 74, 75, 76, the wipers of which normally rest upon contacts corresponding to his line. The sub-station apparatus includes, in addition to the parts previously mentioned, two relays 37, 42, and a bell 50, which serves also as an impedance for the microphone current. The subscriber, having set his drum to the desired number, removes his receiver, thereby locking the drum and shifting the springs 25 - - 32. The closure of springs 25, 26 completes a circuit over spring 10, stepping-magnet 33, and line 82 for the. relay 62, which by closing contacts 64, 65 brings into the line circuit or relay 58, this in turn closing the circuit of a motor driving the interrupter 57, which (when the relay 58 is energized) is included in the circuit over line 82. The magnet 33 is thus intermittingly energized and moves round the ratchetwheel 12 and springs 10, 14 until spring 10 engages the insulating-stud 11 and opens the line circuit. At each energization of magnet 33 the line 83 is earthed, thereby energizing the magnet 72, which moves the wipers one step. During this selecting-operation, a relay 37, energized in parallel with the magnet 33, opens the speaking circuit. The opening of the circuit over line 82 de-energizes relays 62, 58, relay 62 closing momentarily at contacts 67, 66, 68 a circuit for the calling-relay 77 which locks up in a circuit from battery 53, springs 79, 78, relay 77, wiper 75, multiple cable, wiper 75<1> of called line, line 83<1>, and bell 50<1> to earth. A relay 42<1>, energized in parallel with the bell 50<1>, locks up and prevents the establishment of the selecting-circuit at the called station. An auxiliary winding 77<a> on the relay 77 gives a ringing-signal to the calling subscriber. When the called subscriber removes his receiver, relay 77 opens the ringing- circuit and closes the speaking circuit. The microphones are supplied with current through relays 62 (or 62<1>), line 82 (or 82<1>), and the winding of bell 50 (or 50<1>) to earth, the voice-currents passing over the loop circuit and through condensers 95, 95'. When the called party replaces his receiver, his relay 42<1> de-energizes, rendering him free to receive or initiate a call. When the calling party hangs up, the selecting-circuit over line 82 and magnet 33 is completed over spring 14 and contacts 27, 25 to earth. The selector and the springs 10, 14 of the impulse-transmitter are thus operated in synchronism as before, until both reach their normal positions, whereupon the line circuit is opened by spring 14 engaging the insulating-stud 20. If an attempt is made to call a line busy as a called party, the relay 77 of the third party remains energized and prevents completion of the speaking circuit.