Hitachi RAC-10G5, Service Manual, Page: 45 / 62

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4. Initial setting (IC401)
The ratings of the compressor, maximum rotation speed, etc. are preset in the micro computer.
3. Buzzer Circuit
Fig. 3-1 Buzzer Circuit
Fig. 3-2 Buzzer Operation
●
When the buzzer sounds, an approx.
3.9kHz square signal is output from
buzzer output pin
21 of the micro
computer. After the amplitude of
this signal has been set to 12Vp-p
by a transistor, it is applied to the
buzzer. The piezoelectric element in
the buzzer oscillates to generate the
buzzer’s sound.