| 摘要 |
A photoelectric barrier comprises an emitter emitting a movable modulated beam which scans periodically at a high rate an area to be protected. The beam is then redirected to a photoelectric receiver supplying the signal deactivating the machine controls. The barrier also comprises a circuit generating pulses which are effective to suppress some of the pulses emitted by the photoelectric emitter in order to monitor the machine operation during scanning, the suppression pulses being produced by detecting the correct rotation of the scanning motor. |
