Improvements in high frequency duplex signalling systems

Abstract

Abstract 312,079. Lorenz Akt.-Ges., C. May 18, 1928, [Convention date]. Duplex signalling; secret signalling systems; thermionic generators and modulating systems.- In duplex high-frequency signalling, for transmission undamped high-frequency oscillations are produced, periodically interrupted at an inaudible frequency, and modulated in accordance with the signal, and for reception the received modulated, interrupted oscillations are combined with locally produced interrupted oscillations. The undamped oscillations are produced by an oscillating thermionic valve 3 and are interrupted by supersonic oscillations produced by an oscillating-valve 15 and impressed on the grid of the valve 3 across a condenser 8, which is also supplied with signalling-currents from a microphone 17. The interrupting- oscillations, when the apparatus is used for reception, may be out of phase with the received signals, but tuning-means may be provided to bring them into phase. A piezo-electric crystal 19 regulates the frequency of the carrier wave, and a piezo-electric crystal 20 or a tuning- fork controls the frequency of the supersonic oscillations. The crystals at both stations may be changed simultaneously according to a prearranged system to ensure secrecy. A telephone receiver 12 is shunted during transmission, either manually by a key, or automatically by a third winding 21 inserted in a telephone transformer and connected in the microphone circuit.

Inventors

No inventors recorded.

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