Hitachi RAS-25CNH2 Service Manual page 33

2. Receive Circuit
LIGHT
RECEIVING
UNIT
0V
The Light receiving unit receives an 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
computer. 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.
R709
+
C701
ZD701
–
0V 0V
Micro computer
21
Buzzer output
Fig. 3-1 Buzzer Circuit
q
of the micro
Sound wave
12V
R710
R705
C702
0V
Fig. 2-1
12V
R801
BZ
0V
Metal diaphragm
Fig. 3-2 Buzzer Operation
– 36 –
Wireless input
18
Micro computer
BZ1
Q805
Pizoelectric element
V V