Hitachi RAD-25NH7 Service Manual page 46

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2. Receiver Circuit

Light receiving

The light receiver unit receives the infrared signal from the wireless remote control (option part). 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 a transistor, it is applied to

the buzzer. The piezoelectric element in

the buzzer oscillates to generate the

buzzer's sound.

R419

unit

C405

Microcomputer

Buzzer output

Fig. 3-1 Buzzer Circuit

R611

C611

Fig. 2-1

R722

Metal diaphragm

Sound wave

Fig. 3-2 Buzzer Operation

– 56 –

Wireless input

Microcomputer

12V

Q722

Pizoelectric element

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