Patent GB-118691-A (GB)
Title: Improved Automatic Telephone System.
IPC: H04Q5/00
Filed: 1917-09-14
Abstract: 118,691. Stevens, A. E. Sept. 14, 1917. Automatic exchange s y s t e m s ; impulsctransmitters. - In a syetem for private installations, the selector stepping and holding magnets 14, 28 are connected in separate line circuits 13, 30 with earth return, and the bell of the called station is rung over a circuit which is closed momentarily when the impulsesender of the calling station reaches its normal position. Means are provided for giving characteristic bell calls simultaneously at all stations, so that if a party is within sound of any bell on the system and hears his characteristic call, he may reply at any station. Impulse-sender. The impulse-wheel 1 is set before removing the receiver, and is retained set by a spring arm 2 until the receiver is removed. A pin 36 causes the springs 37, 38 to engage momentarily as the wheel reaches its normal position. Operation of selector. The return of the impulse-wheel 1 repeatedly energizes the stepping- magnet 14 over contacts 4, 3, 8. As the selector leaves its normal position, a projection 22 shifts the springs 23, 24, 25, thus energizing the holding-magnet 28 over line 30, transmitter 31, receiver 5, and contact 8. Supply of ringing-current. The resistance of the instruments 5, 31 is too great to allow the magnet 28 to shift the spring 35, but as the impulse-sender reaches normal, the pin 36 momentarily closes contact 37, 38, short-circuiting the instruments 5, 31, so that the magnet 28 is fully energized and retains its armature attracted after the short circuit is removed. Assuming- that station C is called, the ringing-circuit is closed from battery 55, stepping-magnet 54, line 53, bell 50, line 49, contacts 47, 46, selector multiple 44, brush 20 of the calling-station A, contacts 42, 35, 41, 40, 39, line 30, contacts 38, 37, 8, to ground. Talking circuit and supply of microphone current. The talking circuit passes from ground 11 to station A, through the receiver and transmitter, line 30, contacts 39, 40, 41, 42, brush 20, bank wire 44, contacts 46, 47, line 49, and transmitter and receiver at station C, to earth. Microphone current is supplied to both stations from battery 27, through magnet 28 and contacts 25, 23, to line 30, and thence to both stations in parallel. Busy test and signal. If the station C is busy as a calling-party in another conversation, a busy interrupter 69 is connected over the off-normal contacts 67, 46 to the bank wire 44, so that a party trying to call this station receives a busy tone current. If station C is busy as a called party, his bank wire 44 is grounded over the selector brush of the calling-party, and if a third party tries to call station C, the lock-out relay 77 of the third party is energized over contacts 76, 35, 75, 74 and brush 20. The relay 77 closes a holding- circuit over contacts 82 independent of magnet 28, and also connects the busy interrupter 69 over contacts 80, 39 and line 30 to the calling-party. Release. When the calling-party hangs up, the earth is removed from line 30, and the holding- magnet 28 de-energizes, releasing the selector. Simultaneous calls at all stations. If the called party does not reply, the calling-party may move the brush of his selector to engage a terminal 84 connected to a common signal relay 86 controlling a signal circuit having bells 93 bridged across the circuit at all stations on the system. The relay 86 is energized when the pin 36 on the impulsewheel momentarily closes contact 37, 38, and also by the depression of the key 98 by which code rings may be given to attract the wanted party, who may converse with the calling-party from any station by moving the selector individual to that station so that its brush engages the terminal connected to the circuit of the signal relay 86. This feature forms the subject-matter of Specification 118,805.