Abstract: A passive infrared detector, including a pyroelectric sensor with three pairs of contiguous, active elements and a Fresnel lens with a plurality of segments each of which has an optical center and an equivalent focal length, each pair of active elements disposed in different plane, with each optical center juxtaposed to the plane of at least one of those active elements, substantially at the focal length.

Abstract: An amusement device is disclosed which contains a signal generator attached to a flexible member. When the flexible member is repeatedly waved, an oscillatory electrical signal is produced by the signal generator and supplied to a sound generator which produces sound which synchronously varies with the repeated flexure of the member caused by the waving action. The sound generator produces a first tone with respect to the oscillatory electrical signal and a second tone when the frequency of the oscillatory electrical signal exceeds a predetermined value.

Abstract: A hail sensor is disclosed which contains a piezoelectric transducer positioned to produce an output signal when it is vibrated by a hailstone. In one embodiment, the transducer is mounted on a perforated member which is exposed to falling precipitation. In an alternative embodiment, the hailstone impacts a rebound surface and is deflected toward the transducer where an electrical output is produced.

Abstract: A sensing device is disclosed which produces a response when the point of impact between an object and a member occurs at a preselected location on the member. When the member vibrates after being impacted by the object, an oscillatory electrical signal is produced by a piezoelectric sensor. Appropriate circuitry is provided for analyzing the oscillatory electrical signal and for producing a response if the object impacted the member at the preselected location. The sensing apparatus is particularly useful in athletics for determining whether a game object contacted the athletic instrument at its "sweet spot".

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.