英语翻译1、 If we consider binary transmission,the complete information about a particular message will always be obtained by simply detecting the presence or absence of the pulse.By comparison,most other forms of transmission systems convey the

英语翻译
1、 If we consider binary transmission,the complete information about a particular message will always be obtained by simply detecting the presence or absence of the pulse.By comparison,most other forms of transmission systems convey the message information using the shape,or level of the transmitted signal; parameters that are most easily affected by the noise and attenuation introduced by the transmission path.Consequently there is an inherent advantage for overcoming noisy environments by choosing digital transmission.
2、 The reader may ask,how does the demultiplexer know which group of 8-digits relates to channel 1,2,and so on?Clearly this is important!The problem is easily overcome by specifying a frame format,where at the start of each frame a unique sequence of pulses called the frame code,or synchronization word,is placed so as to identify the start of the frame.A circuit of the demultiplexer is arranged to detect the synchronization word,and thereby it knows that the next group of 8-digits corresponds to channel 1.
3、 Noise can be introduced into transmission path in many different ways; perhaps via a nearby lightning strike,the sparking of a car ignition system,or the thermal low-level noise within the communication equipment itself.It is the relationship of the true signal to the noise signal,known as the signal-to-noise ratio,which is of most interest to the communication engineer.
4、 Basically,if the signal is very large compared to the noise level,then a perfect message can take place; however,this is not always the case.For example,the signal received from a satellite,located in far outer space,is very week and is at a level only slightly above that of the noise.Alternative examples may be found within terrestrial systems where,although the message signal is strong,so is the noise power.
5、 So far we have assumed that each voice channel has a separate coder,the unit that converts sampled amplitude values to a set of pulses; and decoder,the unit that performs the reverse operation.This need not be so,and systems are in operation where a single codec is shared between 24,30,or even 120 separate channels.
6、 A high-speed electronic switch is used to present the analog information signal of each channel,taken in turn,to the codec.The codec is then arranged to sequentially sample the amplitude value,and code this value into the 8-digit sequence.Thus the output to the codec may be seen as a sequence of 8 pulses relating to channel 1,then channel 2,and so on.This unit is called a time division multiplexer.

1 ,如果我们考虑到二进制传输,完整的资料,对一个特定信息将始终得到根本探测存在与否的脉搏.相比之下,大多数其他形式的传输系统传递信息,利用信息的形状,或水平的,传送信号的参数是最容易受到噪声和衰减所提出的传输路径.因此是一个潜在的优势,为克服高噪声环境中选择数字传输.
2 ,读者可能会问,请问解复用器知道哪一组的8位数字关乎频道1,2等?很显然,这是很重要的!问题是容易克服的,由指定的帧格式,如果在开始时每一帧一个独特的序列脉冲称为帧代码,或同步字,是放置等,以确定开始的骨架.电路的解复用器是安排检测同步字,从而它知道下一组的8位数字对应通道1 .
3 ,噪音可以引入传输路径,在许多不同的方式,也许途经附近的雷击,引发汽车点火系统,或热低层次的噪音通信设备本身.这是关系的真实信号,噪声信号,为信号与噪声的比例,这是最感兴趣的通信工程师.
4 ,基本上,如果信号是非常大的相比,噪音水平,那么一个完美的信息可以发生,不过,这并非总是如此.举例来说,收到的信号从一个卫星,设在远太空,是非常星期,并在一定的水平上仅略高于就是噪音.另类的例子可发现地面系统的地方,虽然信息的信号强,所以是噪声功率.
5 ,到目前为止,我们还假定每个语音通道有一个单独的编码,单位转换采样振幅值,以一组脉冲和解码器,该单位对其执行反向操作.这无须如此,体制的运作,如果一个单一的codec是分担24 ,30 ,甚至是120个单独的频道.
6 ,一个高速电子开关是用来目前模拟信息信号的每个通道,采取反过来,以编解码器.编解码器,然后安排样品,比上一季度的振幅值,并典这个值到8位数序列.因此,输出到编解码器,可被视为一种序列8脉冲有关渠道1 ,然后第二频道,等等.这股被称为时分复用器.
我能做的只有这么多