Patent ID: 6486777
Filing Date: 2002-11-26
Classification: G08B

Abstract:
A personal monitoring apparatus for monitoring the whereabouts of a subject, the apparatus comprising:a) a portable remote unit connected to the subject, said remote unit including a remote unit power supply, a water sensor comprising a prism light collector responsive to wetting, a light source positioned adjacent a first side of said prism so that light from the light source is collected in said prism and internally reflected toward a second side of said prism to exit therefrom, and a light detector positioned adjacent said second side for detecting the internally reflected light exiting said prism, a radio transmitter for sending a remote unit radio signal substantially responsive to the water sensor, a radio receiver for receiving a base unit radio signal, and a remote unit alarm, wherein said water sensor is positioned so that said prism light collector will become wet when said portable remote unit is immersed in water, the light collection characteristics of said light collector being changed thereby; and b) a base unit in radio communication with the remote unit, the base unit including a base unit power supply, a radio transmitter for sending the base unit radio signal, a radio receiver for receiving the remote unit radio signal, a distance estimator for substantially estimating the distance between the base unit and the remote unit, a base unit alarm responsive to said remote unit radio signal, and a direction finder for generally finding the direction from which the remote unit signal originates relative to said base unit.