| 摘要 |
A signal processing unit of the present invention includes: input terminal ( 21 ) to which an input signal is input; high-pass filter ( 23 ) for cutting off the DC component of the input signal; output terminal ( 22 ) for outputting a signal output from high-pass filter ( 23 ) as an output signal; determination element ( 26 ) for determining whether or not the voltage of the output signal falls out of a predetermined detection threshold range; and, switches ( 27,28 ) for connecting the output node of high-pass filter ( 23 ) to a power supply circuit when the voltage of the output signal is determined to fall out of the detection threshold range at determination element ( 26 ).
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