Kenwood NX-300 Service Manual page 41

8. Signaling Circuit
8-1. Encode (QT/DQT/LTR/DTMF/2-tone/MSK)
Each signaling data signal of QT, DQT, LTR, DTMF, 2-tone
and MSK is generated by the DSP circuit, superposed on
a modulation signal and output from IC108. The modula-
tion balance of the QT/DQT/LTR signal is adjusted by the
D/A converter (IC703) and the resulting signal is routed to
the modulation input of the VCO and VCXO (X500). Each
deviation of the TX QT, DQT, LTR, DTMF, 2-tone and MSK
tone is adjusted by changing the output level of IC108 and
the resulting signal is routed to the VCO and VCXO. The RX
DTMF tone is routed to the receive audio signal system, and
is output from the speaker.
8-2. Decode (QT/DQT/LTR/DTMF/2-tone/MSK)
The audio signal is removed from the FM detection
signal sent to the DSP circuit and the resulting signal is de-
coded.
9. Compander Circuit
The term "compander" means compressor and expand-
er. The compander reduces noise by utilizing a compressor
and an expander. The transceiver contains a DSP (IC102) to
perform this operation. The transceiver 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/LTR/DTMF/2 音 /MSK)
QT，DQT，LTR，DTMF，2 音和 MSK 的各信令信号由 DSP 电路
产生，叠加到调制信号上并从 IC108 输出。QT/DQT/LTR 信号
的调制平衡由 D / A 转换器 ( I C703) 进行调整，产生的信号送
入 VCO 和 VCXO(X500) 的调制输入。TX QT，DQT，LTR，DTMF，
2 音和 MSK 音各自的频偏通过 IC108 输出电平的变化进行调整，
产生的信号被送入 VCO 和 VCXO。RX DTMF 音被送入接收音频
信号系统，从扬声器输出。
8-2. 解码 (QT/DQT/LTR/DTMF/2 音 /MSK)
音频信号从发送到 DSP 电路的 FM 检测信号中移除，产生的
信号被解码。
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。手持对讲机含有
D S P ( I C102)，用以执行此操作。可用 F P U 打开或关闭手持对
讲机的压扩器。
NX-300
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