Hitachi RAS-18YH4 Service Manual page 37

2. Receiver Circuit
VDD
0V
IRR
V
OUT
GND
0V
IRR (light receiver unit) receives the infrared signal from the wireless remote controller. The receiver
amplifie and shapes the signal and outputs it.
3. Buzzer Circuit
Microcomputer
Buzzer output
When the buzzer sounds, an approx 3.9kHz
square signal is output from buzzer output pin 30
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.
12V
Q141
R212
L201
R141
ZD141
C212 C211
0V
0V
R211
R611
Fig.2-1
IC711
30 1
Fig.3-1 Buzzer circuit
RECEIVER I/P
13
C611
Microcomputer
0V
12V
R721
BZ
BZ1
16
Metal diaphragm
Sound wave
– 40 –
Pizoelectric element
V
Fig. 3-2 Buzzer Operation
V