GB291083A - Arrangement for the automatic regulation of the degree of transmission of transmission systems, particularly of high frequency transmission systems - Google Patents

Abstract

291,083. Siemens & Halske Akt.-Ges. May 28, 1927, [Convention date], Fading, preventing ;-Relates to an improved method of automatically regulating the strength of received signals to compensate for fading effects, of the kind described in the Specification 289,050, wherein a control frequency lying outside the signal frequencies is applied at the receiving end to shift the effective grid-bias of a valve receiving both signal and control frequencies. As shown in the Figure, the output circuit of the first valve or rectifier g comprises two filter circuits c, s, the first of which passes the useful signalling frequencies to an amplifier n, whilst the second separates the special control frequency and passes it to the grid of an auxiliary valve h. A resistance r in the output circuit of the latter is also included in the grid circuit of the valve g, and raises or lowers the effective grid potential of this valve in accordance with fluctuation in the received signals due to fading &c. The auxiliary valve h may similarly control the effective grid bias of an amplifier valve inserted before the detector g. When used for a picture transmission, the usual synchronizing frequency may also serve as the gain-control frequency. Alternatively the grid or anode currents of the valve h can be used to control the grid bias of the first amplifier valve, or to operate the mechanical form of control relay described in Specification 289,050.