Abstract: An automatic shut-off device for television sets or equivalent apparatus receiving electromagnetic signals and transforming the same into audio or video signals. A shut-off device includes a detecting circuit which responds to the presence of a video or audio signal on the apparatus to be controlled permitting the set up of a switching circuit in the form of a silicon controlled rectifier energizing a relay in the power circuit of the apparatus or television set. The automatic device includes a time delayed portion simultaneously energized with the detecting portion to provide a timing function through unijunction transistor to control the firing of the silicon controlled rectifier in the operation of the relay.