| 摘要 |
PROBLEM TO BE SOLVED: To prevent the latch up in a reception drive circuit control IC at the time of applying a DC power voltage. SOLUTION: This signal detection circuit comprises a signal input part 9 for detecting an input signal and/or a noise voltage level, a voltage detector 8 for detecting an output voltage level from the signal input part even when the power voltage is not applied, and a transistor array of a PNP transistor Tr1, an NPN transistor Tr2, and an NPN transistor Tr3 for controlling ON/ OFF of the power voltage based on the 'Enable' signal presenting that an output signal from a terminal OUT of the voltage detector 8 and a DC-DC converter circuit 4 is in operation.
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