Abstract: A monitor for restricting the operating time of electronic apparatus, such as a television set, is formed of an outer case of sufficiently small size to set atop a television set. The case includes on its outer surface a display of the time remaining of the predetermined operating time. The case also includes a chamber for enclosing time setting controls, the chamber having a locking cover for securing the controls from tampering by children. A slot in a wall of the chamber permits passing of a power cord of a television into the chamber while preventing the egress of the plug of the cord upon a locking of the cover to the chamber. A timer and power sensor within the case to measure the amount of time that power flows into the television, such power flow being an indication of operating time. A relay within the case switches off the power upon detection of a timing signal indicating conclusion of the predetermined operating time.