GB146988A - High frequency signalling - Google Patents

Abstract

146,988. Western Electric Co., (Assignees of Heising, R. A.). March 3, 1916, [Convention date]. Multiplex wireless signalling.-Wireless signalling is effected by a high-frequency carrier wave modulated by a wave of intermediate and inaudible frequency which is itself modulated in accordance with the signal to be sent. Multoplex working is obtained by employing several non-interfering intermediate frequencies, and, if desired, several carrier frequencies. The transmitting-apparatus shown in Fig. 1 comprises a high-frequency generator 1 with a frequency of, say, 1,000,000, coupled to a, circuit 2. A number of generators 3 ,3<1>, 3<11> &c., of frequencies, say 40,000, 30,000, 20,000 are connected through thermionic modulators 4 to tuned circuits 6 coupled to the circuit 2. The oscillations generated by the sources 3, 3<1>, &c. are modulated by microphones 5 or other source of audible-frequency signal currents. The modulated oscillations in the circuits 6 modulate the carrier wave in the modulator 7, and are amplified by the relay 9 and transferred to the aerial 10. At the receiving-station, Fig. 2, the waves are received in a circuit 13 tuned to the carrier frequency, and are rectified to currents of intermediate frequencies by the detector 14. These currents are separated by the circuits 15, 15<1>, &c. tuned to the various intermediate frequencies, and are transferred to other tuned circuits 16, 16<1>, &c., which are connected across the grids and filaments of detectors 17 having telephones 18 in their output circuits.