| 摘要 |
<p>A light curtain for supervising or controlling the operation of machines comprising a series of electrical light sources arranged to give light pulses which are short in relation to the repetition frequency. After the light pulses have spanned the supervised region they are detected by one or more pulse detectors for each light source. When the detectors associated with each light source receive simultaneous pulses on their inputs a starting pulse for the light source next in sequence in the series is released.</p> |
