UNIVERSALLY ADJUSTABLE AND FOCUSABLE ALARM APPARATUS AND ELECTRIC CIRCUITRY THEREFOR

摘要

Apparatus having a base attachable to a surface. A hollow holder is universally supported by the base and an electric element of a light beam transmitting and receiving circuit is mounted in the holder. The light beam travels through an outer end opening of the holder and fitted to the holder to extend across the outer end opening are a light focusing lens and a light filter. A rheostat is provided in the circuit to adjust the intensity of the light beam. The apparatus has an alarm circuit which is energized when the light beam is broken by an object of a predetermined size and the alarm circuit includes an audible and a visual signalling device as well as a two-way switch for selectively and alternatively controlling the two devices.