Abstract: A switching circuit which facilitates electrically controlled actuation of a switching device, such as a relay, in a two-wire circuit where access may be gained only to an active conductor. The switching circuit includes an electrically actuatable switching device which is arranged to be connected in series with a load in the form of a lamp in a single phase as circuit. A solid state second switching device is connected in series with the first switching device. A first energy storage device is connected across the first and second switching devices and a second energy storage device is connected across the second switching device. Gating circuitry associated with the second energy storage device is provided to effect periodic ON-OFF gating of the second switching device during the time that the first switching device is actuated to a conducting state.

Abstract: A switching circuit which facilitates electrically controlled actuation of a switching device, such as a relay, in a two-wire circuit where access may be gained only to an active conductor. The switching circuit (10) comprises an electrically actuatable switching device (19) which is arranged to be connected in series with a load in the form of a lamp (11) in a single phase ac circuit (18). A solid state second switching device (20) is connected in series with the first switching device (19). A first energy storage device (21) is connected across the first and second switching devices and arranged under controlled conditions to deliver actuating power to an actuating element (22) of the first switching device (19). Also, a second energy storage device (23) is connected across the second switching device (20) and is arranged to provide power for gating the second switching device.

Abstract: A light level sensor for use in controlling the switching of artificial lighting. The sensor comprises a photoelectric transducer which provides an output signal at a level which is significant of the illumination level of incident light. An A-D converter and a microprocessor are located in circuit with the transducer for detecting the level of the transducer output signal and for any cyclic variation of the transducer output signal resulting from cyclic variation of the level of incident light. Further circuit means are provided for generating a sensor output signal if either (a) the level of the transducer output signal is below a predetermined level or (b) the level of the output signal is above the predetermined level and, at the same time, cyclic variations occur in the level of the transducer output signal.