GB316946A - Improvements in and relating to the control of alternating currents, especially those of high frequency - Google Patents

Abstract

316,946. Lorenz Akt.-Ges., C., (Assignees of Pohontsch, M.). Aug. 6, 1928, [Convention date]. Magnetic modulating systems; keying systems. - alternating currents, particularly high-frequency currents employed in wireless signalling, are modulated or interrupted by the use of a pair of iron-cored chokes, one in the aerial or load circuit, and the other in an absorbing circuit with similar constants, not coupled to the aerial circuit. As shown in Fig. 3, the generator circuit, which may be energized directly or through a frequency-multiplier from an alternator 1, or by a valve generator, is coupled by transformers 3, 4 to an aerial circuit V and to an absorbing circuit X. Iron-cored choke coils 9, 18 in the respective circuits are saturated in turn, the transmitting key or microphone, being arranged to vary the direct current in these windings. The windings 13, 19 may be arranged in the plate circuits of a pair of valves V1, V2, Fig. 4. For telegraphy, a keying -device or relay R is arranged to render these valves conductive and non-conductive in turn by biasing their grids, the switches U being in the vertical position. For telephony, the switches U are thrown horizontal to couple the grids of valves V1, V2 to the plates of valves V3, V4, the grids of the latter pair being controlled in push-pull fashion by a microphone circuit M. The purpose of the arrangement is to maintain a constant load on the oscillation generator, and so prevent surges and variations of frequency during the keying or modulating operation.