Hitachi RAI-25NH5 Service Manual page 47

2. Receiver Circuit
12V
R412
R413
The light receiver unit receives the infrared signal from the wireless remote control. The receiver amplifies
G
and shapes the signal and outputs it.
3. Buzzer Circuit
When the buzzer sounds, an approx.
G
3.9kHz square signal is output from buzzer
output pin of the microcomputer. After
30
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.
5V
R411
0V
Microcomputer
30
Buzzer output
Fig. 3-1 Buzzer Circuit
Sound wave
V
DD
R611
V
out
IRR
GND
Fig. 2-1
R722
Metal diaphragm
Fig. 3-2 Buzzer Operation
– 57 –
13 RECEIVER I/P
Microcomputer
0V
12V
BZ
BZ
Q722
0V
Pizoelectric element
V
V