Electrical switching appts. controlling TV CRT - compares detected cumulative operating time with operating time limit to disconnect current supply

摘要

The switching device is connected to the network and the CRT on the input and output sides and has a time measuring and comparison circuit (14) with an associated memory (16) holding a limit time and a cumulative operating time. The operating time of the CRT is determined by a reception device responsive to the energy radiated by the CRT line or image deflection. The reception device pref. uses a synchro-dyne receiver with an oscillator, a demodulator (28), a LF amplifier (30) and an electromagnetic and/or acoustic sensor (32). USE - Disconnecting current when preset operating time limit is reached to limit t.v. viewing by children etc.