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2-8 Band switching circuit
The band switching control signals are outputted from pins 21 and 22 of the CPU and fed to
pins 3 and 4 of the band switching IC.
This IC then outputs
the drive voltage(+l
2V) to the tuner from either
pins 1, 2, 7 or 8
according to input signal.
The table below shows the input/output
logic of the band switching IC.
Antenna
L
Tuner
IC710<LA791 o>
VL
VH
HP
u
Band swit[
4
1
4
2
3
4
7
4
8
Band Switching IC Logic
1
CPU
21
22
I
Input
I
output
I
I
I Pin 3
Pin 4
I Pin 1 Pin 2
Pin 7 Pin 8 I Selected Band I
w
LL
H---
VHF-LOW
HL
-H
--
VHF-High
LH
--H-
Hyper
HH
---H
UHF
-14-
A?-/l
w
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