Electronic article monitor, generating alarm signal

摘要

The system comprises several members, each secured to the article to be protected. The signal transmitter (1) contains a signal generator (3) for a modulated signal by modulating a carrier frequency signal with a modulation signal. The modulation signal is transmitted (4) via a transmit aerial (5). Each attachment member comprises a reception aerial, a signal receiver for selective reception of the modulated signal, and a frequency selector for selecting the modulation signal from the modulated signal. An alarm generator and an alarm block for the generator operation complete the monitoring system.