Improvements in telephone repeater circuit arrangements

摘要

329,033. Callender's Cable &. Construction Co., Ltd., Urmston, J., and Smith, F. S. Feb. 15, 1929. Addition to 321,673. Two-way repeating systems.-In the telephone repeater circuits described in the parent Specification, and comprising a junction transformer 4 - - 6 coupling the incoming, outgoing and twoway lines 1, 2, 3 and an additional coupling transformer 8, 9 between the incoming and outgoing circuits, arranged so that the currents in the outgoing circuit due to the two couplings neutralize each other when currents arrive over the incoming circuit. The winding 8 is connected in the output of an amplifying valve 20, tha input of which is connected to the incoming circuit in parallel with the input of an amplifying valve 15 feeding the junction transformer. The transformer 8, 9 is provided with a third winding 17 associated with a balancing network 18. By this means, currents from line 2 are substantially prevented from penetrating the incoming circuit and reaching the coupling transformer, and the additional coupling does not load the amplifier 15. The valves 20 and 15 should be matched as regards characteristics and operating conditions, small variations in characteristics being compensated by adjustment of the filament currents or by variation of the input voltage, for example by utilizing a tapped transformer, choke or resistance placed across the incoming circuit. The two valves may be combined in a single structure comprising one filament, one or two grids, and a pair of anodes. The invention is described particularly as applied to the arrangement shown in Fig. 3 of the parent Specification, but may be applied to other arrangements described therein.