Abstract: Apparatus and a method for previewing the field of coverage of an infrared sensor and, accordingly, adjusting its position for use in an intrusion detection alarm system. A mirror can be mounted in place of the infrared sensor and has indicia corresponding to beams of sensitivity of the infrared sensor to provide an indication of the beams of sensitivity superimposed on an image reflected by the mirror to aid in adjusting the position of the infrared sensor. Alternatively, or as verification of the sensor position, a photograph can be prepared by use of a camera located in a proposed infrared sensor position. Directional beams of sensitivity of the infrared sensor are plotted on the photograph by the use of a prepared transparent overlay showing the correspondence between areas of the photograph and respective elements of the lens of the infrared sensor. Portions of the sensor lens are masked to block reception of infrared radiation from known sources along beams of sensitivity of the infrared sensor.

Abstract: A switch housing in which a cylindrical hollow body of the housing has attached wing elements, each in the form of a partial cylinder and resiliently movable radially and circumferentially of the body, varying the overall transverse dimension of the housing so that the housing may be removably inserted into cavities of various sizes or non-uniform bore, with the wing elements biased to exert outward force against the interior of a cavity. The wing elements may define exterior threads to aid in retention of the housing in a cavity, and a head of the housing preferably defines a chamfered radially extending flange to limit insertion of the housing, and grooves to aid in removing the housing from a cavity.