Kenwood TK-6110, Service Manual

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17
TK-6110
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.
IC708
DTMF
DECODE
IC709
(2/2)
AMP
IC705
LPF
IC713
AF
IC709 (1/2)
LPF
from IC202
FM IC
2TON
LSD IN
IC604
CPU
STD
DCK
SD
Fig. 13 Decode
CIRCUIT DESCRIPTION
IC901
D913 D912 D914 D915
CH
UP
MON B SCN
CH
DN
A C
Q1 Q3 Q4 Q5
IC604
CPU
CLK,DAT,LCDCS
K1
K2
Fig. 11 Key input
IC604
CPU
LPF SUM
LPF SUM
SUM
VCO2
HSDO
LSDO
TX AUDIO
RX AUDIO
to AF AMP
MOD
IC710
DAC
(ADJ)
Fig. 12 Encode
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.