| 摘要 |
PURPOSE:To prevent malfunction due to a noise and to increase a response speed by generating signals differing in frequency by turns, by setting and resetting an FF when receiving them, and by detecting a change in state. CONSTITUTION:An oscillating circuit 2 generates two signals with frequencies f1 and f2. When light emitted from a light emitting element 4 through the operation of the circuit 2 is photodetected by a photodetecting element 6, an output is generated on a line 40. The signals with the frequencies f1 and f2 in the output are detected by resonating circuits 10 and 11 respectively and then integrated by integral circuits. A comparing circuit 44, when the output of a circuit 19 is greater than that of a circuit 23, outputs a set signal to an FF28; when not, the comparing circuit outputs a reset signal to the FF28. Consequently, the FF28 is set or reset. The output of the FF28 is integrated by an integral capacitor 34 and when the output of the capacitor 34 exceeds the discrimination level of a transistor 37, a load 38 is energized with electric power. |
