Improvements in electric circuits comprising electronic discharge devices

Abstract

Abstract 529,044. Automatic volume control. COSSOR, Ltd., A. C., and JOFEH, L. May 9, 1939, No. 13807., [Class 40 (iv)] [Also in Group XL] In a circuit comprising a pair of grid-controlled valves connected in push-pull and having impedances in their cathode leads so as to provide negative feedback, a variable impedance is connected between the cathodes so as to vary the amount of feedback. Fig. 3 shows an arrangement of resistances in which tappings for grid bias are taken from the cathode resistance and a variable resistance R9 controls the amount of feedback. A reactance may be connected in series with resistance R9 and be variable so that the amount of feedback will vary with frequency. The reactance may be arranged in parallel with the resistance R9, Fig. 5, and may comprise an inductance L1 in parallel with a capacity C3 to provide a dip in the frequency characteristic. Part of the cathode resistances may be common to the two valves and the impedance may be connected between tappings on the resistances instead of between the cathodes. Contrast expansion or contraction may be obtained by providing a resistance that varies with current flow and may comprise a pair of oppositely connected rectifiers in parallel, Fig. 7 (not shown), or a carbon or metal filament lamp. Specification 515,044, [Group XXXVI], is referred to.

Inventors

No inventors recorded.

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