Before we proceed with our study of networks, let us learn about some data communication terminologies being used.
Channel: A communication channel is a medium that is used in the transmission of a message from one point to another. In simple terms we can say that it is a pathway over which data is transferred between remote devices. It may refer to the entire physical medium, such as a telephone line, optical fibre, coaxial cable or twisted pair wire, or, it may refer to one of the several carrier frequencies transmitted simultaneously within the line. Depending on their speed, we have three broad categories of communication channels – narrow band which is slow and used for telegraph lines and low speed terminals; voice band used for ordinary telephone communication and broad band which is fastest and is used for transmitting large volumes of data at high speeds. Bandwidth: In electronic communication , bandwidth refers to the range of frequencies available for transmission of data. It is expressed as the difference in Hertz(Hz) between the highest frequency and the lowest frequency. For example , a typical voice signal has a bandwidth of approximately 3KHz. Wider the bandwidth of a communication system, greater is the capacity and hence greater is the amount of data that can be transmitted over a period of time. In computer networking, bandwidth is often used as a synonym for data transfer rate about which you will read in the next subtopic.