Abstract: A cross-over field-of-view composite Fresnel lens for use in an infrared detection system includes a plurality of Fresnel lens segments provided in first and second groups. The first group of Fresnel lens segments are constructed as grooves-in lens segments and arranged in the array as grooves-in lens segments (or, alternatively, are constructed as grooves-out lens segments and arranged in the array as grooves-out lens segments). The second group of the Fresnel lens segments are constructed as grooves-out lens segments but arranged in the array as grooves-in lens segments (or, alternatively, are constructed as grooves-in lens segments but arranged in the array as grooves-out lens segments).

Abstract: A circuit for operating relay contacts is based upon the utilization of an AC line zero voltage to provide a relay contact closure. The circuit is inexpensive and draws extremely low current levels. The circuit involves a latching arrangement of gates responsive to a zero crossing detector and a Delay Time output from a sensor. The gating circuits function in a latching arrangement which has an adjustable output to energize a relay and in turn provide for the closing of contacts which occurs substantially at zero voltage.

Abstract: A passive infrared intrusion detector is arranged for mounting to the ceiling of a room to be protected. Infrared radiation from points within the room is focused onto an infrared sensing element by a multi-segment dome-shaped lens. The multi-segment lens in a preferred embodiment has central, downwardly facing beams of infrared sensitivity and other beams of infrared sensitivity at multiple azimuth angles at selected elevation angles.

Abstract: A gauge for determining the pitch diameter of threads on pipe and tubing, for determining the taper of a thread on the pin or box end of tubular structures used in oil and gas exploration an production, and for determining the existence of an out-of-round condition at the location of the threads on such tubular structures. The gauge includes an elongated scale rail, a pair of blade blocks slidably mounted on the scale rail, and a pair of thread engaging blades pivotally supported on the blade blocks. Locking and adjusting elements are provided in association with the blade blocks for locking the blade blocks in a fixed spatial relationship to each other along the length of the scale rail, with the distance therebetween precisely adjusted to a predetermined value.