Abstract: An electrical circuit that interrupts normal operation of a cable television channel selection box responsive to unauthorized entry into the box. A closure means is mounted about its periphery by a plurality of screw members that must be removed in a predetermined sequence to avoid disabling the box. A power source provides current through a bypass means in the form of a normally closed switch means as long as the closure means remains closed, but removal of a fastening means not associated with said bypass means prior to interruption of said current results in de-activation of the channel selection box.