Abstract: A frequency source (1) in, for example, a remote unit in a mobile communications system, is controlled to maintain a stable frequency signal. In normal operation, the frequency source (1) is frequency locked to an external reference frequency (10). A temperature detecting device (2) monitors the temperature of the frequency source, and information relating to temperature is stored in a storage device (7) together with information relating to control signals (6) applied to the frequency source (1). In the absence of the reference frequency (10), the temperature of the frequency source (1) is detected and the stored information is used to generate a control signal (6) to control the output frequency of the frequency source (1) in accordance with the detected temperature.

Abstract: A remote data transfer system, particularly an identification system for identifying objects such as livestock, pets and containers. An interrogator generates a directional light beam which the operator can direct at a selected animal or package up to 30-14 200 meters away; and a tag transponder carried by the object is activated only on receipt of the light beam, and transmits a coded RF signal. The signal is received by the interrogator which displays the identity of the animal derived from the coded RF signal. In its "receive" mode, the tag transponder requires minimal power, thereby prolonging battery life. A short rise time light pulse (or a pulse sequence) is identified and used to switch power to the transponder. After transmission of the coded RF signal, the transponder returns to a low power draw stand-by state. The tag is also able to transmit real time information, with or without the tag identity data.

Abstract: A spread-spectrum transmission system wherein a plurality of spread-spectrum signals are frequency division multiplexed by offsetting the center or carrier frequencies of the spread-spectrum signals by a fraction of the spectral-line spacing of the signals. The signals are generated by modulating a carrier with a pseudo-noise (PN) code signal. At a receiver, demultiplexing is carried out by mixing (42) the received multiplexed signal with a plurality of local oscillator frequencies (43) which are offset from each other in the same manner as the centre or carrier frequencies of the multiplexed spread-spectrum signals. The mixed signals are then further mixed (45) with generated PN code signals (47) corresponding to those used to generate the multiplexed spread-spectrum signals. The epoch of each generated PN code signal is then advanced or retarded in response to a respective epoch control signal (48) generated by a respective controller (46).

Abstract: Apparatus for determining the position of a source of electromagnetic radiation relative to a remote object is disclosed. A multicomponent radiating means of unknown orientation is provided having components centered about the origin of the source. A plurality of electrical signals are applied to the components of the multicomponent source to generate a plurality of electromagnetic fields. The electromagnetic fields are multiplied and thus are distinguishable from one another. A multicomponent receiving means is disposed on the remote object. The multicomponent receiving means is provided with at least three orthogonal components for detecting and measuring components of the electromagnetic fields transmitted from the source.