|Broadband in telecommunications is a term which refers to a signaling method which includes or handles a relatively wide range of frequencies which may be divided into channels or frequency bins. Broadband is always a relative term, understood according to its context. The wider the bandwidth, the more information can be carried. In radio, for example, a very narrowband signal will carry Morse code; a broader band will carry speech; a yet broader band is required to carry music without losing the high audio frequencies required for realistic sound reproduction. A television antenna described as "normal" may be capable of receiving a certain range of channels; one described as "broadband" will receive more channels. In data communications a modem will transmit a bandwidth of 64 kilobits per seconds (kbit/s) over a telephone line; over the same telephone line a bandwidth of several megabits per second can be handled by ADSL, which is described as broadband (relative to a modem over a telephone line, although much less than can be achieved over a fiber optic circuit, for example).
Broadband in data communications may have the same meaning as above, so that data transmission over a fiber optic cable would be referred to as broadband as compared to a telephone modem operating at 600 bits per second.
However, broadband in data communications is frequently used in a more technical sense to refer to data transmission where multiple pieces of data are sent simultaneously to increase the effective rate of transmission, regardless of actual data rate. In network engineering this term is used for methods where two or more signals share a medium.
Various forms of Digital Subscriber Line service are broadband in the sense that digital information is sent over one channel and voice over another channel sharing a single pair of wires. Analog modems operating at speeds greater than 600 bit/s are technically broadband. They obtain higher effective transmission rates by using multiple channels with the rate on each channel limited to 600 baud. For example, a 2400 bit/s modem uses four 600 baud channels (see baud). This is in contrast to a base-band transmission where one type of signal uses a medium's full bandwidth such as 100BASE-T Ethernet.