Patent ID: 6388573
Filing Date: 2002-05-14
Classification: G01V,G08B

Abstract:
A motion detection system adapted for use in detecting movement of an object through a threshold in a selected movement direction, comprising:(a) a first transmitter operative to produce a first broadcast signal and to transmit the first broadcast signal across the threshold along a first transmission path; (b) a second transmitter operative to produce a second broadcast signal and to transmit the second broadcast signal across the threshold along a second transmission path, said first and second broadcast signals being out of phase with respect to one another; (c) receiver circuitry operative in an absence of movement of the object through the threshold to receive the first and second broadcast signals and to generate a receiver circuitry reference signal, and operative upon interruption of both the first and second broadcast signals by the object within a selected period of time to generate a receiver circuitry interrupted output corresponding to movement of the object, respectively, through the first and second transmission paths; (d) processing circuitry operative to monitor said receiver circuitry and operative in response to detection of said receiver circuitry interrupted output, corresponding to movement of the object through the threshold in one of a first and second movement direction, to produce an event detection signal; and (e) output circuitry operative to receive said event detection signal and to generate a selected output in response thereto, thereby to indicate movement of the object through the threshold in at least one of the first and second movement directions.