Hitachi RAC-08PH1, Service Manual, Page: 38 / 114

2. Receiver Circuit
IRR (light receiver unit) receives the infrared signal from the wireless remote controller. The receiver
amplifies and shapes the signal and outputs it.
3. Buzzer Circuit
When the buzzer sounds, an approx 3.9kHz
square signal is output from buzzer output pin
of the microcomputer. After the amplitude of this
signal has been set to 12Vp-p by IC711, it is
applied to the buzzer. The piezoelectric element in
the buzzer oscillates to generate the buzzer’s
sound.
Fig.2-1
Fig.3-1 Buzzer circuit
Sound wave
Metal diaphragm
V
Pizoelectric element
V
Fig. 3-2 Buzzer Operation
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