Agc switching network for dual tuners of a tv receiver

Claim 1

In combination with a signal receiver of a type including AGC network means providing an AGC signal and of a type that employs two different tuners each having an AGC signal input terminal; an AGC switching network for supplying said AGC signal to either one of said tuners provided that power also is supplied thereto and for preventing said AGC signal from being supplied to an unpowered one of said tuners, said AGC switching network including first and second transistors each having base, collector and emitter electrodes, means supplying said AGC signal to said base electrodes of said transistors, means connecting said AGC signal input terminal of one of said tuners in a circuit including said emitter and collector electrodes of said first traNsistor, means connecting said AGC signal input terminal of the other of said tuners in a circuit including said emitter and collector electrodes of said second transistor, means for selectively applying a D.C. potential to power said one tuner and to simultaneously apply a forward bias between said base and emitter electrodes of said first transistor, means for selectively applying a D.C. potential to power said other tuner and to simultaneously apply a forward bias between said base and emitter electrodes of said second transistor, whereby application of power to either of said tuners is required to render the one of said transistors connected to said AGC signal input terminal of said tuner to which power is applied conductive to permit said AGC signal to be applied via said conductive transistor to said AGC signal input terminal of said tuner to which power is applied, the other of said transistors remaining unconductive until power is applied to the tuner to which said other transistor is connected.