The carrier used by each pair operates at a unique frequency that does not interfere with the others.
每对装置使用的载波频率唯一的，并彼此互不干扰的频率运行。
Time Division Multiplexing 时分多路复用
@ The general alternative to FDM is time division multiplexing (TDM), in which sources sharing a medium take turn.
与FDM不同的另一种复用形式是时分多路复用(TDM)，按这种方式，各发送源轮流使用共享的通信介质。
For example, some time-division multiplexing hardware use a round-robin scheme in which the multiplesor sends a packet from sourcel, then sends a packet from souces2, and so on. round-robin 循环
例如，某些TDM硬件使用循环法方案共享介质，用这种方法，多路复用器先发送源1的一个包，然后发送源2的一个包，如此循环。 Figure 6-2 illustrates the idea. 图6-2说明了这种思想。
@ Dividing data into small packets ensures that all sources receive prompt service because it prohibits one source from gaining exclusive access for an arbitrarily long time.arbitrary
prompt 立刻地 prohibit禁止 arbitrarily 任意地 exclusive 独占 把数据分成许多小包保证了所有源都接受到即时服务，因为它禁止一个源任意长时间独占介质”。
In particular, if one source has a few packets to send and another has many, allowing both sources to take turns sending packets guarantees that the source with a small amount of data will finish promptly.
特别是，如果一个源只有少量的包发送，而另一个源有许多包发送，于是允许两个源轮流发送包就保证只有少量数据的源会很快结束。
@ In fact, most computer networks use some form of time division multiplexing. demultiplexor
实际上，大多数计算机网络使用某种形式的TDM。