Icom IC-F2721 Service Manual page 14

4-6-2 FRONT CPU (FRONT UNIT; IC3)
Pin Port
number name
7 RES Input port for rest signal.
KR0– I n p u t p o r t s fo r t h e 1 0 - k e y p a d .
19–22
KR3 (IC-F2800 series only)
Output control signals for LCD back-
light.
LIGT1,
28, 29
LIGT2
47 LEDT Outputs control signal for the TX LED.
48 LEDR Outputs control signal for the RX LED.
DICK, Input ports for control signal from the
51, 52
DIUP dial (S9). (IC-F2700 series only)
KYUP, Input ports for control signal from [ ],
53, 54
KYDN [ ] keys. (IC-F2800 series only)
Input port for the microphone hanger
detection signal.
57 HANG
Low: While microphone on the
Input port for the PTT switch of the
58 PTT
connected microphone.
KYP0– Input por ts for the programmable
59–63
KYP4 function keys (P0–P4).
4-6-3 D/A CONVERTER (MAIN UNIT; IC8)
Pin Port
number name
Outputs AF signal to the squelch cir-
2 SQL
cuit (IC12, pin 8).
Outputs modulation signals to the
3 MOD
VCO circuit.
10 TENC Outputs CTCSS/DTCS signals.
Outputs deviation balance control sig-
11 BAL
nal.
Outputs beep audio signals to the
14 BEPV speaker via the AF amplifiers (IC34,
IC38).
Outputs AF signals to the speaker via
15 SIGNAL
the AF amplifi ers (IC34, IC38).
22 TONE Outputs single tone signal.
Outputs reference oscillator (X2) con-
23 REF
trol signal.
Description
LIGT1 LIGT2 LIGHT
HIGH HIGH DIM
HIGH LOW OFF
LOW HIGH ON
LOW LOW OFF
hanger.
Description
4-6-4 D/A CONVERTER (MAIN UNIT; IC30)
Pin Port
number name
1 T1
2 T2
3 TXLVA
4 RXLVA
4 - 7
Description
Outputs the bandpass filters (D23,
D26, D68, D69) tuning signal.
• While receiving
Outputs the bandpass filters (D17,
D18) tuning signal.
• While transmitting
Outputs the TX power control signal
which selects TX output power of
HIGH, LOW1 or LOW2. The output
signal is applied to the APC amplifi er
(IC37, pin 1).
Outputs TX VCO lock voltage.
Outputs RX VCO lock voltage.