Abstract: There is disclosed herein a transducer for acoustic communications through a series arrangement of fluid and solid media, the transducer comprising: —a signal processor configured to implement a communications scheme at and around a center frequency of at least 1 MHz; a piezoelectric element for activation in accord with the communications scheme; an electrode electrically connected to the signal processor, and being attached to the piezoelectric element; and a substrate, having the piezoelectric element mounted thereon, wherein an aspect of the electrode at the piezoelectric element is approximately equal to the acoustic wavelength of an acoustic wave in the substrate at the center frequency. There is further disclosed a remote monitoring device employing at least one of the transducers described, in concert with a further transducer. Still further, there is disclosed a method of communicating using the transducer described herein.

Abstract: There is disclosed herein a transducer for acoustic communications through a series arrangement of fluid and solid media, the transducer comprising: a signal processor configured to implement a communications scheme at and around a centre frequency of at least 1 MHz; a piezoelectric element for activation in accord with the communications scheme; an electrode electrically connected to the signal processor, and being attached to the piezoelectric element; and a substrate, having the piezoelectric element mounted thereon, wherein an aspect of the electrode at the piezoelectric element is approximately equal to the acoustic wavelength of an acoustic wave in the substrate at the centre frequency. There is further disclosed a remote monitoring device employing at least one of the transducers described, in concert with a further transducer. Still further, there is disclosed a method of communicating using the transducer described herein.

Abstract: An apparatus and method are provided for monitoring, remotely, information relating to the motion of at least one moving object. The apparatus comprises: means for illuminating a retro-reflective data carrier mounted on each moving object, in particular when the moving object is located at a predetermined monitoring position; means for detecting, in optical signals returned by the retro-reflective data carrier, data representing a timing trigger and data representing an identifier for the at least one moving object; timer means responsive to a timing trigger detected at the predetermined monitoring position to trigger a timer associated with a detected identifier; and an output to provide timing information associated with the detected identifier, and hence relating to the at least one moving object at the predetermined monitoring position. The timing information may be used to derive relative ordering, relative timing or speeds of moving objects, for example.