Signaling Circuit; Compander Circuit; Encode (Qt/Dqt/Dtmf/Msk); Decode (Qt/Dqt/Dtmf/2-Tone/Msk) - Kenwood TK-5710 Service Manual

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TK-5710 B

8. Signaling Circuit

8-1. Encode (QT/DQT/DTMF/MSK)

Each signaling data signal of QT, DQT, DTMF and MSK is
generated by the DSP circuit, superposed on a modulation
signal and output from pin 16 of the CODEC IC (IC724).
The modulation balance of the QT/DQT signal is adjusted
by the D/A converter(IC738) and the resulting signal is routed
to the modulation input of the VCO and VCXO (X400).
The each deviation of the TX QT, DQT, DTMF and MSK
tone is adjusted by changing the output level of the CODEC
IC and the resulting signal is routed to VCO and VCXO. The
RX DTMF tone is output from pin 15 of the CODEC IC,
passes through the receive audio signal system, and is out-
put from the speaker.

8-2. Decode (QT/DQT/DTMF/2-tone/MSK)

The audio signal is removed from the FM detection signal
sent to the DSP circuit and the resulting signal is decoded.

9. Compander Circuit

The term "compander" means compressor and expander.
The compander reduces noise by utilizing a compressor and
an expander.
The transceiver contains DSP IC (IC715) to perform this
operation. The transceiver compander can be turned on or
off using the FPU.
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CIRCUIT DESCRIPTION