| 摘要 |
A switch controlled by a light curtain formed of a large number of rapid, intermittent, sequentially flashed, light beams which, when interrupted, actuate the switch. The light beams are flashed back and forth between a pair of spaced apart columns each having a row of alternating light transmitters and receivers so that a beam of light from one transmitter of one column is received by an opposing receiver in the second column, in turn causing the next transmitter in the second column to send a beam of light to the next receiver in the first column, and so on back and forth to the ends of the columns and then repeating the same cycle again. When any of the beams of light is interrupted, as by inserting a physical object in its path, the switch is actuated. By arranging the transmitters and receivers, in each column, in pairs (i.e., two transmitters, then two receivers, etc.) and connecting them into odd and even, sequentially operated, rows in each column, the light beams may be relatively wide or non-sharply focused, so that the operation of the system, is relatively uneffected by misalignment.
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