Elkron EL250RT Notice D'installation Et D'utilisation page 61

At the end of the operation, remove the attenuating screen once you are certain that you have found the optimal
setting.
N.B. If the barriers are to be aligned with optical synchronization, for absolute certainty that the optics are truly
aligned (with no false alignments caused by gate photocells), cover the optics with your hand: a continuous beep
indicates that the beam detects another infrared source.
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EL250RT