Hitachi RAS-EH36PHLAE Service Manual page 69

4. Buzzer Circuit
• When the buzzer sounds, an approx.
3.9kHz square sigl).8.l is output from
buzzer output pin ®of the micro
computer. After the amplitude of this
signal has b een 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.
5. Remote control reception circuit
[Typical communication waveform]
R e mo t e co n trol r e c ep tion i n p ut
( pin@ofmicrocomputer )
_Be _ e _ p _ ( r e _ c _ e p _ ti _ o n _ t _ o _ n e _ ) ____
Enlarged reception waveform
5Vlm
:LL
• An infrared signal from the remote control unit is converted to an electrical signal by the remote
control light-receiving unit and is received by the microcomputer. Data is transmitted as
digital data O and 1 by changing the interval of the basic pulses at about 420
Microcomputer
Buzzer output
Fig.4 - 1 Buzzer Circuit
/
Sound wave -f11J���
�
12V
R22
Q22
R24
C22 C21
ZD24
ov
I ,. -------, - 1
Approx.400 ms.
. .
-----
71U1111)11111111111111111111111111111111
--1 g
LI
Lill
Appm<120 us.
Fig.5-2
12V
OV
Metal diaphragm
V
Fig.4-2 Buzzer Operation
+
Fig.5-1
-�-----
,....
I
----------
69
Piezoelectric element
,----c1+
V
ov
µs.