| 摘要 |
The barrier 1 comprises a transmission unit placed at one side of a track and having a plurality of infrared light emitting diodes 5 which are multiplexed and modulated at a predetermined frequency, a reception unit 6 placed at an opposite side of the track and having a plurality of infrared photoreceivers 7, and an electronic apparatus 8 for managing the electric signals generated by the photoreceivers 7. The apparatus 8 comprises an electronic unit 14 for the automatic determination of a corresponding reference value Vf for each of the photoreceivers 7, for comparing the signals generated by the photoreceivers 7 with said reference value Vf, and for verifying said comparison so as to signal the condition of the barrier, whether free or blocked by an object. <IMAGE> |
