A remote unit can be controlled by sensing the change of impedance in the power line of a control unit as the control unit is turned on. The power line circuit includes a portion of an oscillator which is damped by the turn-on. Functions such as power turn-on and temporary audio muting are possible with...http://www.google.fr/patents/US4435844?utm_source=gb-gplus-shareBrevet US4435844 - Remote control circuit
