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.

Abstract: A system for controlling the connection of power from a main supply (11) to electrical devices (22) by way of switching devices (19). The system includes a low voltage, direct current power supply (10), a plurality of command units (15) connected to and powered from the power supply by way of an electrical connection (14), and a plurality of switching devices (19) connected to and powered from the power supply by way of the electrical connection (14). Each of the command units (15A, 15B and 15C) is arranged to generate a uniquely coded pulse-form command signal to a central processing unit (18) by way of the electrical connection (14), and the central processing unit is arranged to generate pulse-form actuating signals having codes determined by the command signals. The central processing unit is arranged to feed the actuating signals to the switching devices (19) by way of the electrical connection (14).

Abstract: A timing device which is associated with a light level sensor and which is arranged to provide a time-out signal to a relay after a predetermined time has elapsed following detection of a low light condition and initial energization of the relay. The device provides for synchronization of an initiation time T.sub.1 and, hence, a time-out signal generating time T.sub.2 with respect to a periodically occurring event time T.sub.3 (for example, sunset time) in order that the desired time of generating the time-out signal might be re-established following interruption of power to the device. Should loss of power occur, the last entered event time T.sub.3 is employed to synchronize the initiation time T.sub.1 and, hence, the signal generating time T.sub.2, when detection of a predetermined light level next occurs following re-establishment of power to the device.

Abstract: A method of and apparatus for controlling the opening and/or closing of contacts of an electro-mechanical switching device in an alternating current circuit. Detection is made for the existence of a voltage having a level which is indicative of a back emf in a load circuit immediately following opening of the contacts, and if such a voltage level is detected an incremental adjustment is made in the phase angle at which successive actuations of the contacts are effected. This procedure is repeated under the control of a microprocessor until such time as the voltage which is indicative of back emf reduces to zero, this providing an indication that contact opening is occurring at a time corresponding to zero current crossing in the alternating current waveform.

Abstract: A power supply which incorporates a high frequency inverter and which is suitable for use in conjunction with a florescent lamp. The power supply comprises a full wave rectifier (10) and a reservoir capacitor (12) connected across the rectifier for the purpose of providing successive half-cycles of the voltage waveform V2 across the capacitor with a minimum instantaneous voltage level greater than zero. A solid state switching device (14) and an oscillator (15) are connected in circuit with the reservoir capacitor. The oscillator generates a gating signal to the switching device. The switching device is arranged to provide an output voltage V4 which has a frequency determined by the applied gating signal V3 and which has a peak amplitude value which varies over successive cycles with the waveform of the voltage V2 across the reservoir capacitor.

Abstract: An apparatus for determining the relative positions of power outlets within a multi-outlet electrical circuit and, specifically, for determining the first occurring power outlet in a multiple-earth-neutral power system in which earth and neutral wires are interconnected at a distribution point. The apparatus incorporates circuitry for generating a current pulse and probe means for injecting the pulse into a wiring loop which extends between neutral and earth contact terminals of each of the power outlets. The probes are also employed for detecting the voltage drop which occurs along the wiring loop as a consequence of the current flow through the loop, and circuitry is provided for generating a signal which is representative of the voltage drop along the wiring loop.