Kenwood NX-720 Service Manual page 27

8. Signaling Circuit
8-1. Encode (QT/DQT/DTMF/2-tone/MSK)
Each signaling data signal of the QT, DQT, DTMF, 2-tone
and MSK is generated by the DSP circuit, superposed on a
modulation signal and output from the ASIC (IC507). Each
deviation of the TX QT, DQT, DTMF, 2-tone and MSK tones
are adjusted by changing the output level of the DSP (IC502)
and the resulting signal is routed to the VCO and PLL.
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
by the DSP.
9. Compander Circuit
The term "compander" means compressor and expander.
The compander reduces noise by utilizing a compressor and
an expander. The DSP (IC502) performs this operation. The
Compander can be turned on or off using the FPU.
CIRCUIT DESCRIPTION / 电路说明
8. 信令电路
8-1. 编码 (QT/DQT/DTMF/2 音 /MSK)
DSP 电路生成 QT、DQT、DTMF、2 音和 MSK 的各信令信号，
这些信号被叠加到调制信号上并从 ASI C (I C507) 输出。TX
QT、 DQT、 DTMF、 2 音和 MSK 音各自的频偏通过改变 DSP (IC502)
的输出电平进行调整，产生的信号被送至 VCO 和 PLL。
8-2. 解码 (QT/DQT/DTMF/2 音 /MSK)
音频信号从发送到 DSP 电路的 FM 检测信号中提取，产生
的信号由 DSP 解码。
9. 压扩器电路
"Compander"一词表示压缩器和扩展器。压扩器利用压缩
器和扩展器减低噪音。DSP (I C502) 用以执行此操作。可用
FPU 开启或关闭压扩器。
NX-720
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