GB146881A - Improvements in wireless signalling systems - Google Patents

Abstract

146,881. Western Electric Co., (Assignees of Arnold, H. dc F.). Dec. 1, 1915, [Convention date]. Wireless telegraphy and telephony.-In signalling systems in which high frequency carrier waves of frequency Q and a signalling wave of frequency P are impressed upon a modulator to produce in its output circuit modulated carrier waves which may be regarded as composed of three waves of frequencies Q, Q + P, and Q-P, a. resonating system is associated with the output circuit of the modulator to suppress the unmodulated component Q, or the unmodulated component Q to. gether with one of the modulated components Q + P or Q - P. Fig. 1 shows a wireless trans. mitting station arranged according to the invention. Carrier waves of frequency Q, generated by the oscillating valves, are impressed upon the input circuit of the modulator 5, the amplifying power of which is varied in accordance with the waves of signal frequency P in the microphone circuit 2. Modulated carrier waves in the output circuit of valve 5 are impressed upon an intermediate resonating system consisting of the resonant circuit 7, tuned to the carrier frequency Q, and a pair of resonant circuits 8, tuned to the frequencies Q + P and Q - P respectively. The system presents a small impedance to waves of frequency Q + P and Q - P, but a substantially infinite impedance to waves of frequency Q, thereby preventing the passage of unmodulated current of carrier frequency. Waves of the two transmitting frequencies, Q + P and Q - P are amplified by the amplifiers 10, 12, and delivered to the aerial 14. In a receiving system, Fig. 2, for use in connexion with this transmitter, power is transferred from the aerial 15 to a system of resonant circuits similar to that used in the transmitter, comprising a circuit 17 tuned to the carrier frequency Q, and a pair of circuits 18 tuned to the frequencies Q + P and Q - P. This system is coupled to the circuit 20, which receives oscillations of carrier frequency Q from the generator 26, and is coupled to a detector 22 through a transformer 21. By suppressing, in addition, one of the modulated components, Q + P or Q - P, the system may be used for secret transmission of messages. The invention may also be applied to ordinary line telegraphy or telephony. Specification 102,503 is referred to.