Abstract: A data communication device for attachment to an object is provided having a flexible substrate, a transmitter adapted to transmit data in the form of electromagnetic radiation and a programmable memory. The device has a controller for controlling the transmission of the data and a programming means for programming the device. A power source for the device comprises a power storage device and a power extraction means capable of extracting power from the environment in which the data communication device is located when in use. A data communication system is also disclosed comprising the device and a reader for receiving electromagnetic radiation from the device. The reader includes a perceptive filter adapted to distinguish radiation received from the device from radiation received from other sources.

Abstract: A brush assembly comprising an electrically insulating plate having therein an aperture with which communicate first and second slots. The slots each slidably receive a brush and a compression spring acts between the closed end of each of the slots and the respective brush to urge the brush slidably towards the aperture. The brushes and at least one wall of each of the slots are provided with mating surfaces whereby the brush may be latched in a retracted position relative to its respective slot against the action of its respective compression spring.