Patent ID: 6011468
Filing Date: 2000-01-04
Classification: E05F,E05Y,G07C,G08B

Abstract:
A warning apparatus, comprising:a sensor;a transmitter system which transmits at least one signal electrically connected to the sensor; andan indicator circuit, comprising:an alarm system that provides an alarm signal;a first receiver, which is tuned to a first signal of the at least one signal from the transmitter system, wherein the first receiver is able to receive the first signal from the transmitter system up to a first effective range;a logic device which receives input from the first receiver and provides output to the alarm system, wherein the logic device signals the alarm system to generate an alarm, only when the first receiver receives the first signal from the transmitter system and the indicator circuit is closer to the transmitter system than a first distance and further from the transmitter system than a second distance.