GB153301A - Improvements in amplifier connecting apparatus for telephonic installations - Google Patents

Abstract

153,301. Siemens & Halske Akt.-Ges. Oct. 31, 1919, [Convention date]. Thermionic relays and repeaters.-In a thermionic repeater, each line F1, F2 is provided with a speech-current amplifier R1, R2 in a normally inoperative condition, and with a control amplifier R<1>1, R<1>2. Under the influence of incoming speech currents over the line F1, the amplifier R<1>1 operates to bring the speech-current amplifier R, to an operative state, but reduces the control relay R<1>2 of the outgoing line F2 to an inoperative condition, thus maintaining the amplifier R2 inoperative during the transmission of speech in the direction F1-F2. Similarly, the amplifier R1 is maintained inoperative during transmission in the direction F2-F1. Speech currents arriving over the line F1 are amplified and rectified by the valves R<11>1 and R<1>1, and produce an increased potential drop across an adjustable resistance W1, in the anode circuit of the valve R\. As the grids of the amplifier R1 and of the control valves R<1>2, R<11>2 of the outgoing line F, are connected to opposite ends of the resistance W1, this potential variation results in the amplifier R, becoming operative and the valves R<1>2, R<11>2 being maintained in an inoperative condition. Speech currents are thus amplified by the valve R1, which is arranged to work on the straight portion of its characteristic, but are unable to return through the valve R2. The resistance W1 is shunted by a condenser C, to produce slow voltage fluctuations across the resistance. The speech currents are amplified by the valves R<11>1, R<1>1 to such a degree that for all values of speech current a saturation current flows in the anode circuit of the valve R<1>1 and the potential drop across the resistance W1 is constant. The control amplifiers may be situated away from the speech amplifiers, for instance at the subscribers' stations. In a modification described, a current increase in the anode circuit of a control valve, due to incoming speech currents, is made to operate a contact relay which connects a battery to the grid circuits of the incoming-line speech-current amplifier and the outgoing-line control amplifier to render these operative and inoperative respectively. The amplifiers may also be thrown into and out of operation by connecting or disconnecting the corresponding anode batteries.