Abstract: The present invention provides a tracking system in which a mobile tag having an unknown position, which tag is to be tracked in space over time, transmits a signal comprising a pair of tones at different frequencies. The transmitted signal is received at each of three receivers, each having a known location, where the phase of each of the tones within the signal is measured. The measured phases are passed to a processing unit which determines the position of the tag at the time of transmission of the signal on the basis of the difference between the measured phases of the two tones. The tracking system operates over a defined finite range to track the position of the mobile tag uniquely in space.

Abstract: A position determining system in which a mobile tag having an unknown position is tracked in space over time. In use, the mobile tag either transmits or receives signals including a pair of tones at different frequencies from a number of base stations having known locations. The phase of each of the received signals is then measured and the measured phases are then passed to a processing unit which determines the position of the tag at the time of the transmission of the signals on the basis of the difference between the measured phases of the two tones. In one embodiment, this system is combined with a conventional phase-based position measurement which is derived from phase measurements of similar tones transmitted between the mobile tag and different base stations.

Abstract: A free space point-to-point signaling system is described in which optical beams generated by two free space transceiver units are optically aligned with each other using beam steering techniques. Once aligned, each transceiver unit detects the received signal strength and transmits this information to the other transceiver unit. This information is used by the other transceiver unit to vary the signal strength of the beam that it transmits and to optimise the alignment between the light beams transmitted by the two transceiver units. The determined received signal strength measure is also used to detect if the two transceiver units have become misaligned or if the beams have been interrupted, so that the transmission power can be reduced if necessary or so that the alignment procedure can be restarted.

Abstract: A position determining system in which a mobile tag having an unknown position is tracked in space over time. In use, the mobile tag either transmits or receives signals including a pair of tones at different frequencies from a number of base stations having known locations. The phase of each of the received signals is then measured and the measured phases are then passed to a processing unit which determines the position of the tag at the time of the transmission of the signals on the basis of the difference between the measured phases of the two tones. In one embodiment, this system is combined with a conventional phase-based position measurement which is derived from phase measurements of similar tones transmitted between the mobile tag and different base stations.

Abstract: The present invention provides a tracking system in which a mobile tag having an unknown position, which tag is to be tracked in space over time, transmits a signal comprising a pair of tones at different frequencies. The transmitted signal is received at each of three receivers, each having a known location, where the phase of each of the tones within the signal is measured. The measured phases are passed to a processing unit which determines the position of the tag at the time of transmission of the signal on the basis of the difference between the measured phases of the two tones. The tracking system operates over a defined finite range to track the position of the mobile tag uniquely in space.

Abstract: There is described a manufacturing system comprising a production system operable to process starting materials to output a product. In an embodiment, the manufacturing system includes a sensor which is operable to generate a data signal representative of a parameter of the production system, the sensor having associated therewith a signalling device comprising a retro-reflecting modulator which receives an incoming light beam from a good signalling device associated with a system manager, modulates the incoming light beam in accordance with the data signal, and retro-reflects the modulated light beam conveying the data signal back to the second signalling device.