GB111649A - Improvements in Wireless Telegraphy and Telephony. - Google Patents

Abstract

111,649. Western Electric Co., (Western Electric Co.). Sept. 12, 1917. Addition to 102,503. Wireless signalling.-Relates to wireless signalling systems of the kind described in the parent Specification, in which a wave of radio frequency Q is modulated by a signal wave of audible frequency P so as to produce a resultant wave which may be regarded as composed of three waves of frequencies Q, Q + P, and Q - P, radiation of frequency Q being prevented and signalling being effected by waves of frequencies Q + P or Q - P, or both; the effect of the wave of frequency Q is introduced at the receiving station by a local generator of that frequency. According to the present invention telephony is effected as in the prior invention by waves of frequencies Q+P or Q-P, (where P is the mean speech frequency) and telegraphy is simultaneously effected by restoring the wave of frequency Q at the transmitting-station, In the transmitting arrangement shown in Fig. 1, a generator 1 of radio frequency and a microphone 2 are coupled by means of transformers 3, 4 to a thermionic modulator 5, the output circuit of which is coupled to a system of tuned circuits 7, 8. The branch 7 is tuned to the frequency of the generator 1 and serves as a short circuit to currents of that frequency. The parallel circuits 8 are tuned to offer a large impedance to currents of the generator frequency Q and a low impedance to currents of frequencies differing therefrom by the frequencies occurring in speech, Q Π1'. The circuits 8 are coupled by transformer 9 to amplifiers 10, 11 and the antenna 12. Telephony is thus effected without radiation of waves of frequency Q. Telegraphy is effected by the key 13 which connects the generator 1 through transformer 14 direct to the amplifiers 10, 11. At the receiving station, the circuit 17, Fig. 2, is tuned to frequency Q so that the telegraph signals are led through a detector 18 to the telegraph receiver 19, while the parallel circuits 20 are similar to the circuits 8, Fig. 1. Current of the frequencies used for telephonic transmission are combined with energy of frequency Q from the local generator 22, and are led to the detector 21 and telephone receiver 23.