Kenwood TK-6110 Service Manual page 17

CLK,DAT,LCDCS
IC901
Q1 Q3 Q4 Q5
D912 D913
CH
MON
UP
CH
A
DN
Fig. 11 Key input
8. Signalling Circuit
8-1. Encode
The CPU (IC604) transmits the encode data selected by
the program.
• Low-speed data (QT, DQT)
Low-speed data is output from pin 34 of the CPU. The
signal passes through a low-pass filter consisting of IC706
(2/2), and goes to the summing amplifier (IC711 1/2). The
signal is mixed with the audio signal and goes to the VCO
(L517).
• High-speed data (DTMF)
High-speed data is output from pin 35 of the CPU. The
signal passes through a low-pass filter consisting of IC706
(1/2), and provides a TX DTMF tone and a RX DTMF tone
including a beep tone. The TX DTMF tone is passed to the
D/A convertor (IC710) for DTMF deviation adjustment, and
then applied to the audio processor (IC713).
The signal is mixed with the audio signal and goes to the
VCO. The RX DTMF tone is passed the D/A convertor
(IC710) for audio control summing amplifier (IC711 2/2), au-
dio power amplifier and then to the speaker.
RX AUDIO
HSDO
LPF SUM
IC604
CPU
LPF SUM
LSDO
Fig. 12 Encode
CIRCUIT DESCRIPTION
IC604
CPU
D914 D915
B SCN
K1
C
K2
to AF AMP
SUM
IC710
DAC
(ADJ)
TX AUDIO
VCO2
MOD
8-2. Decode
• Low-speed data (QT, DQT)
The demodulated signal from the FM IC (IC202) is ampli-
fied by IC709 (2/2) and passes through a low-pass filter
(IC705) to remove audio components. The signal is input to
pin 28 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 FM IC (IC202) is ampli-
fied by IC709 (2/2) and goes to IC708, the DTMF decoder.
The decoded information is then processed by the CPU.
During transmission and standby, the PD terminal is High.
When the line is busy, the PD terminal becomes Low, the
power down mode is canceled and decoding is carried out.
• High-speed data (2-tone)
The demodulated signal from the FM IC (IC202) is ampli-
fied by IC709 (2/2) and passes through an audio processor
(IC713) and low-pass filter (IC709 1/2) to remove a low-
speed data.
The CPU digitizes this signal, performs processing such
as DC restoration, and decodes the signal.
IC709
from IC202
(2/2)
FM IC
AMP
DECODE
Fig. 13 Decode
TK-6110
IC713 IC709 (1/2)
2TON
AF LPF
IC604
CPU
IC705
LSD IN
LPF
STD
IC708
DCK
DTMF
SD
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