PROXIMITY SENSING SECURITY SYSTEM

摘要

A security system (5) uses a base unit and a portable transceiver (30) to provide automatic monitoring of a secure perimeter. An intrusion sensor (10) activates a transmitter (20) for emitting a selected frequency wave energy challenge transmission (80) upon the detection of an intruder either outside the perimeter or entering the perimeter. If the intruder has the portable transceiver (30) present to receive the challenge transmission, it automatically emits a responsive wave energy signal (90) as an acknowledgment. A base unit receiver (40) detects the acknowledgment signal and prohibits alarm action. If no acknowledgment signal is received, then either a warning or an alarm is triggered at the base unit. The several distinct wave energy signals can include radio frequency electromagnetic, and audible or ultrasonic acoustic waves. An advantage of acoustic transmission is that the system disarms itself automatically only when the portable transceiver is within a precisely defined distance of the base unit.