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在长途通信中提高接收端的信杂比,这是最根本的问题,也是最主要的问题.国际电报电话咨询委员会(CCITT)建议G143—B对以前每公里3PW的国际电路,经过多次转接杂音电平达不到-44dbmp值时(dbmp表示杂音计加权,相对于1毫瓦功率电平的分贝数),应考虑加装压缩—扩展器,国际无线电委员会(CCIR)也有类似的建议.根据CCITT文献报导,它正在研制性能比较完善的压缩—扩展器,用于以上电路.
Increasing the signal-to-noise ratio at the receiving end over long-haul communications is the most fundamental and most important issue. The International Telegraph and Telephone Consultative Committee (CCITT) recommends that G143-B, after a number of transitions to international circuits that used to be 3PW per kilometer Compromise expanders should be considered when the noise level does not reach the -44dbmp value (dbmp indicates noise meter weight, relative to the decibel power level of 1 milliwatt). Similar recommendations are made by the International Radio Committee (CCIR). According to the CCITT literature, it is developing a more sophisticated compression-extender for the above circuit.