Abstract: The invention concerns LED arrays of the type in which one or more “strings” of LEDs such as 6 are series connected across a potential difference as at 8, 10. To compensate for changes in forward voltage of individual LEDs 4, and/or for supply voltage variations, a switching means (which may be formed as a transistor T2, T3) is provided for selectively removing one or more LEDs from the strings. This can for example be done by selectively shorting the chosen LEDs.

Abstract: An apparatus is disclosed for monitoring usage of multiple electrical devices. The apparatus comprises multiple non-invasive current sensors for sensing current in respective conductors associated with the electrical devices. Such conductors may for example be the electrical power supply leads to the devices. The apparatus further includes multiple analogue to digital conversion functions for digitizing the output from the respective current sensors. A microprocessor is arranged to receive the digitized current sensor and is programmed to create usage data relating to the respective electrical devices. Such usage data may include cumulative elapsed running time. The microprocessor has an associated memory in which the usage data is stored in association with corresponding data identifying the electrical devices. The system further includes an interface through which the usage and identifier data are extractable, to provide usage information for the respective electrical devices.

Abstract: A method and control circuit are disclosed for controlling light emitting diodes (“LEDs”). Based upon the LED's current versus intensity characteristic and temperature versus intensity characteristic, the rate of change of LED output intensity with respect to current is calculated. Adjusting LED current to provide zero rate of change ensures that LED output is maximised.

Abstract: A controller 1 and a control arrangement are disclosed in which the controller 1 serves to intermittently interrupt an AC supply to a device 7 thereby to encode a control signal in the supply. A detector 5 receives the AC supply, decodes the control signal and controls the device 7 in dependence thereupon. Hence only the AC supply lines are needed to supply both power and the control signal. The device may in particular be an aircraft light.