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本文介绍了公用电话网中,用于数传的信道模拟特性各参数(包括衰减频率失真、群时延失真、随机噪声、脉冲噪声、瞬断、幅度突变、相位突变、谐波失真、相位抖动、频率偏差和电平波动)的产生原因和对数传的影响,及其测量原理和国际标准。并例举了北京某机务站至某地机务站(来回长度约2800km)的租用话路(共四个四线音频转接段)的环路测试结果。
In this paper, the parameters of the analog characteristics of the channel for digital transmission, including attenuation frequency distortion, group delay distortion, random noise, impulsive noise, momentary discontinuity, sudden change of amplitude, phase mutation, harmonic distortion, phase jitter , Frequency deviation and level fluctuation) and logarithmic impact, as well as its measuring principle and international standards. And gave an example of the loop test result of a leased road (a total of four four-wire audio transitions) from a Beijing depot to a local depot (round-trip length of about 2,800 km).