Abstract: An acoustic switch for controlling at least two functions of an auxiliary device, such as a television receiver, coupled thereto. A monostable device and a bistable device are coupled to a single tuned transducer. The monostable device is switched from a stable state to an unstable state for a predetermined time interval in response to the reception of an acoustic signal by the transducer. The bistable device is enabled only during the time interval in which the monostable device is in its unstable state. If a second acoustic signal is received by the transducer during this time interval, it switches the bistable device from a first stable state to a second stable state to control one function of the auxiliary device (e.g., power on and off to the television receiver). If a second acoustic signal is not received by the transducer during the monostable time interval, the return of the monostable device to its stable state is used to control another function of the auxiliary device (e.g.

Abstract: A remote control unit for an electrical appliance includes a pair of photocells and one or more threshold devices connected to sense differential illumination of the photocells. The threshold devices, in turn, emit signals that initiate operation of a control device connected to the appliance. The threshold devices are preferably gaseous discharge lamps whose light outputs are sensed by radiation-response switching circuitry.