GB530679A - Improvements in or relating to inter-communication telephony by carrier system - Google Patents

Abstract

530,679. Diplex wireless signalling. HARDINGE, J. H. C. VON D., and ALEXANDER, C. G. March 11, 1939, No. 903. [Class 40 (v)] Intercommunication carrier telephony over power wires is effected between several stations by each station transmitting on a carrier of a frequency pertinent to the distant receiver, and for calling purposes modulating the carrier with a frequency pertinent to itself. The drawing shows in its upper part the transmitter and in its lower part the receiver of any one station. The output of the microphone M is amplified by valve V1 (section b) and is applied to a modulator valve V2 (section a), in the anode circuit of which is a speech coil controlling the modulation of a carrier oscillator V1 (section a), the frequency of which is selected by a switch S1 set according to the distant station. For calling purposes valve V1 (section b) is used as an audio frequency oscillator, the oscillations of fixed frequency being determined by a winding of the transformer Tl and a condenser C5. Anode current for the transmitter is supplied by valve V2 (section b). Incoming signals are applied to a valve V3, the anode d1 acting as a demodulating diode, the anode and grid b as an audio frequency amplifier and the anode d2 as a gain control diode, the output from this valve is amplified further by the valve V4 (section a) and applied through a high pass filter to a speaker S. Incoming calling signals, which are lower in frequency than speech currents are applied to tuned circuits C11, T3 and operate neon call indicators, which indicate the station originating the call. Anode current for the receiver is supplied by valve V4 (section b).