Abstract: The intrusion detection system comprises a pair of narrow-beam microwave detectors exploiting Doppler effect and independently operating. A processing unit analyses the signals received by both detectors versus time and Doppler frequencies and amplitude. Analysis of such data allows detecting an actual intrusion. The processing unit also analyses the steady presence of the radio-frequency signal at each detector, to ascertain possible failures or tampering of the system.

Abstract: An electronic intrusion detection system for monitoring environments having at least one electronic sensor responsive to movements occurring in the environment and adapted to modify at least one characteristic of its electrical output in response to the presence of a moving body in the environment. An alarm is signaled when the modification meets a predetermined condition. A transducer is provided for continuously converting the modification of the output from the electric sensor into a signal that can be perceived by a human being. An alarm control unit connected to the alarm and transducer forwards the signals to the surveillance personnel through a telephone line.