Anti-theft security sensor assembly

Abstract

To provide an anti-thief security sensor assembly wherein an optical axis of a beam projecting unit can be accurately aligned with that of a beam receiving unit, the anti-thief security sensor assembly includes a beam projecting unit for projecting an infrared beam IR and a beam receiving unit for receiving the infrared beam IR. The beam projecting unit includes a projector cover A detachably mounted on a mounting base A for enclosing and protecting a sensor circuit on the mounting base A, an opening detecting switch for detecting a physical opening of the projector cover A, and a projected beam suppressing circuit operable in response to detection by the opening detecting switch to reduce a quantity of the infrared beam emitted from the beam projecting unit to thereby reproduce the infrared beam of a quantity substantially equal to that having passed through the projector cover A. The beam receiving unit includes a receiver cover detachably mounted on a mounting base for enclosing and protecting a sensor circuit on the mounting base , an opening detecting switch for detecting a physical opening of the receiver cover and a received beam level suppressing circuit operable in response to detection by the opening detecting switch to lower the level of the beam signal received by the beam receiving unit to thereby reproduce reduction of the amount of the received infrared beam caused by the receiver cover