Kenwood NX-200 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 (X1). Each deviation
of the TX QT, DQT, LTR, DTMF, 2-tone and MSK tone is ad-
justed by changing the output level of IC108 and the result-
ing 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(X1) 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-200
41