Gate circuit for central control of CATV system

摘要

A gate circuit for use in switching an interference signal in a CATV system whereby the output impedance of the gate circuit is constant, independent of the switching state of the gate circuit. The inventive gate circuit includes input and output transformers, an interference signal being applied to a primary of the input transformer and the secondary of the output transformer being coupled to one input of a coupler receiving as another input an unjammed television signal. A first diode switching circuit controls a signal path between a secondary of the input transformer and the primary of the output transformer in response to an interference control signal. An impedance element having an impedance equal to the characteristic impedance of the transmission lines and the like of the CATV system is connected to the output terminal of the gate circuit via a second diode switching circuit operating in response to the interference control signal for electrically coupling the impedance element to the output terminal when the signal path between the input transformer and the primary of the output transformer is open.