Abstract: A security system is disclosed which senses a variety of activities which affect a secured area and/or the boundary which defines it and identifies particular activities rather than merely indicating that some activity is present. A transducer comprising an electroded ferroelectric film of polyvinylidene fluoride (PVDF) serves as a transducer which provides different output signals in response to different stimuli and responds simultaneously to thermal and mechanical activity. A signal processor separately recognizes the signals produced in response to different activities and identifies the activities detected. An alarm processor controls the system and generates alarm signals in response to the detection of specific activities.