Abstract: An intrusion detection system for a space secured in part by a deflectable physical barrier includes a cable sensor mounted on the barrier in such manner that it stretches and flexes in response to deflection of the barrier, thereby to produce an output signal representing such movement. A signal processor receives the signal from the coaxial cable and provides an output affirmative signal if the amplitude of the cable signal, within a predetermined frequency range lying below about 30 Hz, exceeds a predetermined level for a predetermined time interval.

Abstract: A sensor post has a hollow interior and a semi-rigid surface which flexes in response to an applied force. Sensor bars are mounted to the semi-rigid surface in a cantilevered fashion, and include an intermediate electrically insulated section located inside the interior of the sensor post. The sensor element mounting means is rigidly mounted to a portion of the sensor post which remains essentially stationary during an intrusive event. Sensing elements are made of a flexible semi-conductive sensing material, whose resistance increases when the material is stretched, and are mounted so as to straddle an electrically insulated section of the sensor bars. A signal analysis means detects an increase in the resistance of the sensing elements and generates an alarm.