The total amount of information that can be transmitted through any telecommunications channel is measured in bits per second. Sometimes this is referred to as the baud rate. A baud is a binary event representing a signal change from positive to negative or vice versa. The baud rate is not always the same as the bit rate. At higher speeds a single signal change can transmit more than one bit at a time, so the bit rate generally will surpass the baud rate.

One signal change, or cycle, is required to transmit one or several bits per second; therefore, the transmission capacity of each type of telecommunications medium is function of its frequency, the number of cycles per second that can be send through that medium is measured in hertz. The range of frequencies that can be accommodated on a particular telecommunications channel is called its bandwidth. The bandwidth is the difference between the highest and lowest frequencies that can be accommodated on a single channel. The greater the range of frequencies, the greater the bandwidth, and the faster channel's transmission capacity compares the transmission speed and relative costs of the major types of transmissions media.

One signal change, or cycle, is required to transmit one or several bits per second; therefore, the transmission capacity of each type of telecommunications medium is function of its frequency, the number of cycles per second that can be send through that medium is measured in hertz. The range of frequencies that can be accommodated on a particular telecommunications channel is called its bandwidth. The bandwidth is the difference between the highest and lowest frequencies that can be accommodated on a single channel. The greater the range of frequencies, the greater the bandwidth, and the faster channel's transmission capacity compares the transmission speed and relative costs of the major types of transmissions media.