Patent ID: 7639117
Filing Date: 2009-12-29
Classification: G07C

Abstract:
1. An identification token reading system comprising: an identification token reader configured to read a token when energized; and an object presence sensor including a radiation emitter configured to emit a first radiation and define a field of view the radiation emitter generating a synchronization signal; a radiation receiver configured to receive a second radiation reflected from an object positioned within the field of view, the receiver generating a first signal; a band-pass filter coupled to the receiver and operable to pass a portion of the first signal having a signal level, the synchronization signal operable to coordinate the timing of the band-pass filter and the radiation emitter; and a comparator configured to receive the portion of the first signal and generate a second signal when the signal level increases above a first predetermined level and, to generate a third signal when the signal level falls below a second predetermined level that is lower than the first predetermined level and is greater than zero, the identification token reader being energized in response to receipt of the second signal and de-energized in response to receipt of the third signal.