Icom IC-756PROIII Service Manual page 20

(8) MAIN-A unit; IC3653
Pin Port
number name
Outputs strobe signals for the out-
BSTB put expander ICs (RF-B unit; IC301,
13
IC302).
Outputs the antenna connector
ANTS ([ANT1] or [ANT2]) select signal.
14
High : When the [ANT2] is selected.
Outputs strobe signals for the output
FSTB
15
expander (CTRL-A board; IC11).
Outputs strobe signals for the D/A
ASTB
16
converter (IC3751).
Outputs strobe signals for the output
MSTB
17
expander ICs (IC3752, IC3753).
Outputs control signal for the AF mute
switch (IC331).
AFMS
18
High : When the [AF] control is set to
Outputs squelch mute control signal,
SQLS applied to the squelch gate (IC301).
19
High : When squelch is closed.
(9) MAIN-A unit; IC3654
Pin Port
number name
Outputs squelch control signal for the
SQSS [MIC] and [ACC1] connectores.
12
High : Squlch opend. (RX LED ON)
Outputs control signal for the internal
SPS speaker ON/OFF select relay (RL351).
13
High : Internal speaker is ON.
Outputs strobe signals for the optional
SSTB
14
UT-102 SPEECH SYNTHESIZER.
Outputs chip select signal for the
VCS
15
audio recoder (IC3001).
Outputs external antenna tuner (AH-3)
start signal.
ESTA
16
Low : When the [TUNE] switch is
DSFR, Outputs control signal for the DSP IC
17, 18
DSFW (DSP-A board; IC2001).
Description
maximum counter clockwidth.
Description
pushed.
(10) MAIN unit; IC3752
Pin Port
number name
NBS
4
MSL1
6
MSL2
7
VOSL
12
MISL
14
(11) MAIN-A unit; IC3753
Pin Port
number name
AMS
4
PHFS
5
P50S
6
MODS
7
DSRS
11
FMNS
14
3 - 14
Description
Outputs control signal for the noise
blanker switch (Q3751, Q3752).
High : When the [NB] switch is ON,
except in FM mode.
Outputs audio select signal for the TX
monitor function.
High : During monitoring in SSB or
RTTY mode.
Outputs audio select signal for the TX
monitor function.
High : During monitoring in AM or FM
mode.
Outputs analog switch (IC3005) con-
trol signal for the audio recoder's
(IC3001) output.
High : When the audio recoder's out-
put to the AF circuit.
Outputs analog switch (IC3002) con-
trol signal for input of the microphone
amplifier (IC461).
High : Except the microphone input is
selected.
Description
Outputs AM mode select signal for
the AGC and APC circuit.
High : When AM is selected.
Outputs HF band RF power control
signal.
High : When 0.03–29.999999 MHz
band is selected.
Outputs 50 MHz band RF power con-
trol signal.
High : When 30–60 MHz band is
selected.
Outputs 2nd IF filter (FI131 or FI133)
select signal.
High : When transmitting in AM or FM
mode. (FI131 is ON)
Outputs reset signal for the DSP cir-
cuit and etc.
Outputs FM deviation control signal.
High : When FM-N is selected.