Communication channels are an essential element of every communication system. These channels actually carry the data from one computer to another. There are two categories of communication channels. One category connects sending and receiving devices by providing a physical connection such as a wire or cable. The other category is wireless.

　　通信管道对于每一个通信系统来说是一个至关重要的元素。这些管道实际上把数据从一台计算机传输到另一台。有两个类别的通信管道。一类是有线，另一类是无线。