Monitoring system for mobile person, uses transmitters attached to person and gives alarm if person leaves area in signal range of central receiver

摘要

The monitored person carries a transmitter unit (Z). The transmitter output (11) is usually a coded radio signal, but may be an infra-red or other light signal. The central receiver (O) has an adjustment (13) which can be preset to vary the distance at which an alarm will be generated. The output (12) of the receiver is fed to an alarm system.