Every transmitted signal comprises a spectrum of frequencies, known as its bandwidth. Bandwidth, measured in Hertz (Hz), varies depending on the signal’s information content and quality. For instance, an analog voice signal for standard fixed telephone line quality (enough to recognize the speaker) spans from 300 to 3400 Hz, resulting in a 3,100 Hz bandwidth. While the human voice produces higher frequencies, this bandwidth strikes a balance between signal quality and width. Audio transmission requires a broader bandwidth of around 20 kHz. In contrast, a television signal’s bandwidth is approximately 5 MHz, or 5,000,000 Hz.

Bandwidth, coupled with noise, significantly influences the capacity of a telecommunications channel to carry information. In the context of digital channels, ‘bandwidth’ is sometimes used interchangeably with ‘data rate’ or ‘bit rate’, although they are related but distinct concepts.