Patent ID: 7164119

Claim:
A security sensor system for detecting an object when the latter intercepts passage of a sensing beam, which system comprises: a beam projecting unit including a beam projector for projecting the sensing beam and a drive circuit for driving the beam projector; and a beam receiving unit including a beam receiver for receiving the sensing beam, wherein the beam receiving unit also includes a received beam level detector for detecting a level of the sensing beam received, a level setting circuit for setting a proper range of the received beam level, a request signal output circuit for outputting a request signal requesting an adjustment of an amount of the sensing beam projected from the beam projector in the case that the received beam level departs from the proper range, and a transmitter for transmitting the request signal to the beam projecting unit; and wherein the beam projecting unit also includes a beam projecting power adjustor operable in response to the request signal from the beam receiving unit to drive the drive circuit to thereby adjust an amount of the sensing beam, projected from the beam projector, so that the received beam level can fall within the proper range.