Abstract: A wired program distribution tamper detection circuit useful in CATV including pay T.V. systems which is connected in the subscriber drop cable between the trunk and a subscriber's pay T.V. security device, e.g. descrambler, filter, or converter, or T.V. set and cuts off the program signal in the event the cable is momentarily disconnected as would occur during tampering. The circuit detects an abnormal impedance, in its general form, or the interruption of a d.c. path through the cable, in its preferred embodiment, and inhibits the application of the signal upon such detection. A complaint by the subscriber thus effects an announcement of the tampering.