TK-3180
12
7-2. Decode
■
Low-speed data (QT, DQT, LTR)
The demodulated signal from the IF IC (IC200) is amplified
by IC600 (1/2) and passes through a low-pass filter (IC607) to
remove audio components. The signal is input to pin 128 of
the CPU.
The CPU digitizes this signal, performs processing such as
DC restoration, and decodes the signal.
■
High-speed data (DTMF)
The DTMF input signal from the IF IC (IC200) is amplified
by IC600 (1/2) and goes to IC607, the DTMF decoder. The
decoded information is then processed by the CPU. During
transmission and standby, the DTMF IC is set to the power
down mode.
LPF
LPF
HPF
DTMF
DECODE
AMP
COM-
PARATOR
HSDIN
10
128
LSDIN
IC201
AMP
IC600
IC305
DTRLOAD
STD
DTRCLK
DTRDO
XIN
XOUT
X600
IC607
IC502
CPU
■
High-speed data (2-tone, 5-tone)
The demodulated signal from the IF IC (IC200) is amplified
by IC600 (1/2) and passes through an audio processor (IC607)
and amplifier IC604 (1/2) and comparator IC604 (2/2) to re-
move a low-speed data. The CPU digitizes this signal and
decodes the signal.
■
MSK
The MSK input signal from the IF IC is amplified by IC600
(1/ 2) and goes to pin 5 of IC607. The signal is demodulated
by MSK demodulator in IC607. The demodulated data goes
to the CPU for processing.
8. Power Supply Circuit
BB is supplied via a 3A fuse from the battery ter-
minal connected to the TX-RX unit. Power supply (+B) is ap-
plied to the four AVRs. IC402 supplies 5V (5M) to the control
circuit. IC401 and IC403 supplies 5V to common circuits.
IC406 supplies to the TX circuit, the RX circuit and common
circuits. During transmission, 5TC becomes Low and Q406
is turned on to supply 5V (5T) to the TX circuit. During recep-
tion, 5RC becomes Low and Q405 is turned on to supply 5V
(5R) to the RX circuit.
The power supply voltage monitor IC (IC400) monitors
power supply voltage (+B). If the voltage falls (less than
5.6V), the VOUT port goes “LOW” level, the CPU INT port
also goes “HIGH” level, and the CPU stops.
VIN
VOUT
VDD
OUT
IC400
VIN
CE
IC402
VOUT
RESET
INT
PSW
Power SW
VIN
CE
VOUT
VIN
CONT
VOUT
VIN
CONT
VOUT
SAVE
5RC
Q405
Q409
Q406
5TC
5T
5R
5CNS
5C
IC401
IC403
IC406
Q408
5M
D405
IC405
IC502
CPU
Q401
Q407
Q502
D403
RF power amp
+B
F400
3A
Fig. 13
Decode
Fig. 14
Power supply circuit
CIRCUIT DESCRIPTION