Icom IC-24AT Service Manual page 10
Dual band fm transceiver
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Also See for IC-24AT:
- Instruction manual (44 pages) ,
- Service manual (51 pages) ,
- Instruction manual (44 pages)
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3-6-2
I/O
EXPANDER
1C
PORT
ALLOCATIONS
IC1 (lO
UNIT)
PORT
No.
PIN
No.
TERMINAL
NAME
DESCRIPTION
Q17
4
VCPC
Outputs
power
saver
signal
to
cut the loop
filter
from
the
VHP
PLL
1C.
Q18
5
UCPC
Outputs
power
saver
signal
to
cut the loop
filter
from
the
UHFPLLIC.
Q19,
Q20
6,
7
P01,
P02
Output
RF
output
power
selecting
signal.
Q21
14
V5C
Becomes "LOW" when
selecting the
VHF
band.
This
port
is
controlled with
the
power
save
function.
Q22
13
U5C
Becomes "LOW" when
selecting the
UHF
band.
This
port
is
controlled with
the
power
saver
function.
IC2
(lO
UNIT)
PORT
No.
PIN
No.
TERMINAL
NAME
DESCRIPTION
Oil
6
UBAN
Becomes "LOW" when
the
UHF
band
is
selected.
012
7
TR5
Becomes
"HIGH"
while
transmitting
and
"LOW"
while
receiving.
Q14
13
VT5
Becomes "LOW"
while
transmitting
in
the
VHF
band.
015
12
UTS
Becomes "LOW"
while
transmitting
in
the
UHF
band.
016
11
T+5
Becomes
"HIGH"
while
transmitting.
IC6
(LOGIC
UNIT)
PORT
No.
PIN
No.
TERMINAL
NAME
DESCRIPTION
03
6
AFON
Becomes
"HIGH"
to
open
the
squelch
for
beep
tone.
04
7
RMUT
Becomes
"HIGH"
to
cut
the
AF
signal
while
beep
tone
emits.
05
14
MICM
Becomes
"HIGH"
to
mute
the
microphone
input.
06
13
TXLED
Becomes
"HIGH"
to
light
up
DS4
in
red while
trans-
mitting.
3-6-3
S-INDICATOR
COMPARATOR
CIRCUIT
(LOGIC
UNIT)
The
CPU
indicates
the
2nd
IF
signal
level
as
the
S-indicator
(S-meter)
to
the
LCD
(DS1)
when
the
SIN
port
(pin
2)
is
at
"LOW."
The
S-indicator signal
coming
from
the
DET
UNIT
is
applied
to
the
meter comparator
(IC2, pin 3).
Pin
2
of
the
meter
comparator
receives
a
counting
signal
from
the
CPU
(pins
3-6).
The
counting
signal
is
increased step
by
step.
The
comparator
(pin
1) is
at
"HIGH"
when
the counting
signal
is
lower than the
S-indicator signal
and
becomes "LOW"
when
the counting
signal
is
higher
than
the S-indicator
signal.
When
the
comparator
(
IC2
,
pin
1
)
becomes
"LOW,"
the
CPU
detects
that
the
signal strength
level
is
the
same
as
the
counting
signal
level,
and
indicates
the counting
signal to
the
LCD.
S-INDlCATOR CIRCUIT
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3-5
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