| 摘要 |
A counter installs infrared LEDs(f1-f4) on the one side of stairway and photo sensors(g1-g4) on the other side of it. The counter counts the number only when person gets off and the light is cut off by person in sequence order. This can distinguish the size of person by installation of LEDs(f5-f6) and sensors(g5-g6) at the top of the stairway. The counter records th number with an output of sensor in an inverse state of flip-flop circuit according to the variation of width of compared signal proportional to gate logic circuit and cut off time width of beam entered in the sensor.
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