Hitachi RAF-25FX8 Service Manual page 92

Fig. 3-1 shows the interface circuit used for the indoor and outdoor microcomputers to communicate with each other.
5V
R813
R812
C802
Q803
C805
C803
C804
0V
0V
C821 R821
I/F 0V
C822
D101
0V
Terminal board
D C
D C
Terminal board
5V
5V
R807
IC801
7
R810
R811
R806
Q802
5V
5V
5V
5V
R822
R826
R824
D821
3
1
2
R823
IC801
R825
C823
0V
0V 0V
Indoor P.W.B.
Outdoor P.W.B.
(Communications from outdoor microcomputer to indoor microcomputer)
(Communications from indoor microcomputer to outdoor microcomputer)
Fig. 3-1 Indoor/outdoor interface Circuit
5V
R805
R803
5
6
R804
C801
Q801
0V
0V
0V
5V
R829
R827
R830
Q821
R828
0V
0V
– 110 –
IF transmit
50
output(TXD2)
Microcomputer
IF receive
49
input(RXD2)
C824
0V