Patent GB-344606-A (GB)
Title: Improvements in and relating to telephone systems
IPC: H04Q1/446
Filed: 1930-01-25
Abstract: 344,606. Automatic exchange systems. SIEMENS BROS. & CO., Ltd., Caxton House, Tothill Street, London, MOORE, A. T. C., 87, Boscombe Road, Southend-on-Sea, and CHRISTIAN, D. A., Morven, Charlton Road, Charlton, London. Jan. 25, 1930, No. 2673. [Class 40 (iv).] In a system using voice-frequency control and supervisory signals, the signals are effective immediately during the setting-up of a connection, but after it has been set up are effective only if they persist for a definite time. First system, Fig. 1. Voice-frequency current, e.g. 700-cycle current produced by a thermionic generator, normally flows in the junction TL and is cut off by AY when the junction is seized. At the automatic end BAR falls and BB, BRA pull up to prepare the selector. The dialling key energizes AQ which disconnects the impulse relay from the repeating coils to prevent inductive effects in the junction, and dialled impulses are repeated by AY, BAR. The first impulse operates BD which disconnects the repeater coils from the circuit to the selector during dialling. When the called party replies, BY cuts off the tone generator, energizes BC which shunts the impulse contact bar 2 to render ineffective any chattering by BAR during conversation, and BX which completes the talking circuit and disconnects the rejector circuit. At the manual end AAR falls and AB, ARA pull up signalling the operator and disconnecting the rejector. When the called party clears, BY falls releasing AB, ARA to give the clearing signal and when the operator clears BB, BRA fall sluggishly in succession and release BC and the switches. 2nd system, Fig. 2. On the seizure of the junction AY, AF pull up to connect the tone generator to it. At the automatic end BAR, BB, BG, BRA, BL, BM, BN are operated to prepare the selector and finally BF connects the tone generator to the junction operating AAR, AB, ARA, AK at the manual end. The dialling key operates AQ which disconnects the impulse relay from the repeating coils. The digits are repeated by AY, AF, BAR. BD disconnects the leads to the selector from the repeating coils during dialling. When the called party replies, BY releases BF to cut off the tone generator and energizes BQ which starts the successive operation of sluggish relays BRE, BRC, BRB. At the manual end however AB, ARA fall back and AX pulls up to complete the talking circuit and release AF and the tone generator is thus cut off and BAR at the automatic end prevents operation of BRB and releases BRC, BRE, BB, BG, BRA. BL, BM, BN however are held up. When the called party clears, BY, BX fall and BF connects up the tone generator. AAR, AB, ARA pull up cutting off AX to signal the operator and energize AF which connects up the tone generator. BAR then causes the sluggish operation of BB, BG and finally BRA. When the operator clears AY, CO, AK, AF fall back and then BAR which releases the switch train, and starts the release of all operated relays at both ends. If the operator clears prematurely, AY, CO, AK, AX fall and when the called party clears BY causes BL, BM, BN to fall back sluggishly releasing the switches, and starts the release of the remaining relays. If the junction is re-seized before the previous called party has cleared, CO, AY, AF pull up and BAR responding to the tone currents causes operation in succession of BB, BG, BRA and also of BRE, BRC, BRB. The last mentioned releases BL and BM, BN fall releasing the switch train.