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在选址通信中,采用数字式增量调制有其显著的特点:设备简单;便于利用数字集成电路而达到小型化;抗干扰力强;便于采取加密措施等。在有中继设备的通信网中更便于信号的再生而不增加噪声和失真。当数码率较低时,采用各种改进型的增量调制,可在不同程度上增大其动态范围,以满足一定的电话质量要求。采用话音控制开关,可减少脉冲发射数。而采用低的数码率和采取减少脉冲发射数的措施,可以增加选址通信中同时通话台数。我们的一次调制采用准线性数字式压伸增量调制(见清华大学学报七三年第二期)。它可以在低的数码率情况下,明显地改善话音质量。现对这种调制器的原理、电路及应用作一介绍。
In site communications, the use of digital incremental modulation has its salient features: simple equipment; easy to use digital integrated circuits to achieve miniaturization; strong anti-interference; easy to take encryption measures. Reproduction of signals is facilitated in communication networks with relay devices without adding noise and distortion. When the digital rate is low, the use of a variety of improved incremental modulation can be increased in varying degrees to its dynamic range to meet certain telephone quality requirements. Using voice control switch, can reduce the number of pulse emission. The use of low digital rate and take measures to reduce the number of pulse emission, you can increase the number of simultaneous calls site selection communication. Our first modulation uses quasi-linear digital stretching increment modulation (see Journal of Tsinghua University, 1973, No. 2). It can significantly improve voice quality at low bitrates. Now this modulator principle, circuit and application for an introduction.