Hitachi Summit RAC-50YH5, Service Manual

Page: 54 / 113

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2. Receiver Circuit
The light receiver unit receives the infrared signal from the wireless remote control. The receiver amplifies
and shapes the signal and outputs it.
3. Buzzer Circuit
Fig. 3-1 Buzzer Circuit
Sound wave
Metal diaphragm
V
Pizoelectric element
V
Fig. 3-2 Buzzer Operation
Microcomputer
Buzzer output
BZ1
12V
0V
R721
30 1 16
BZ
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.
12V
R1
0V
0V
13 RECEIVER I/P
Microcomputer
R211 R611
IRR
GND
V
out
V
DD
ZD141
11
6
C
Fig. 2-1
30
8
21
2
C
11
2
C
R141
Q141
R212
L201