GB183416A - Improvements in radio signalling systems - Google Patents

Abstract

183,416. National Pneumatic Co., (Assignees of Rowntree, H.). July 16, 1921, [Convention date]. Secret and selective signalling systems; thermionic oscillation generators and modulating systems; aerials. -Telegraphic or telephonic signals are transmitted and received on two or more carrier frequencies simultaneously. The transmitting and receiving aerial circuits are branched to permit tuning to each carrier frequency. The oscillations are produced by one or more valve generators and signalling is effected by a single key or microphone. The signals are received in a single receiving instrument which adds the effects due to the several frequencies. Fig. 3 shows one form of transmitting-apparatus, and Fig. 1 a receiving-apparatus. The transmitting. aerial 1 \s earthed through two inductances 4, 5 in parallel, each being shunted by a tuning-condenser 6, 7. The tuned oscillating-circuits 9, 11 and 8, 10, in which oscillations of different frequencies are generated, are coupled respectively to the correspondingly-tuned branches 5, 7 and 4, 6. A single key or microphone breaks up or modulates the oscillations in both circuits. At the receiving-station, a similar branched aerial and coupled circuits are employed and are connected to separate valve detectors 25, 26 having a telephone 80 in a common branch of their output circuits. If heterodyne reception is employed, the valve detectors are connected for self-oscillation, each being adjusted to produce the same beat note. As transmitting-apparatus, a single reactively-coupled valve may be used, two separately-tuned circuits being connected in parallel in the plate circuit. The grid potential is varied for modulating by a microphone coupled through a transformer.