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在电话早期,长途电话通信由架空明线或地下对绞电缆上传送音频信号实现的.加感负荷,电缆平衡及放大等技术的应用,在一定范围内改进了这些电路的性能.但是由于需要增加通信容量而又不求助于增加电缆设备,导致最初的频分多路复用电话设备在联合王国的采用.最早的系统,一段时间叫有线的无线电话,但后来通称为载波系统,作为临时性,没有操作或性能的通用标准.第一个系统,载波系统1号,安装于1932—1933年,即在架空线路的音频上面提供一个单路载波话路.在以后几年采用了多种不同的设计,使电路数增加,直至1936年第一套12路载波设备开始运行.与此同时,负回授电子管放大器出现了,因而
In the early days of telephony, long-distance telephone communications were carried over overhead lines or underground twisted-pair cables to transmit audio signals.The application of techniques such as load sensing, cable balancing and amplification improved the performance of these circuits to some extent, but due to the need to increase Communications capacity without resorting to the addition of cable equipment, resulting in the initial adoption of the FDM telephone equipment in the United Kingdom.The earliest system, a period of time called a wired radiotelephone but later known as a carrier system, was used as a temporary , With no common standards for operation or performance.The first system, Carrier System # 1, was installed in 1932-1933 to provide a single carrier talkback on overhead lines of audio, using a number of variations over the next few years Design increased the number of circuits until the first set of 12 carrier devices became operational in 1936. At the same time, the negative feedback tube amp appeared and thus