The various forms of digital subscriber line (DSL) services are broadband in the sense that digital information is sent over multiple channels. In the late 1980s, the Broadband Integrated Services Digital Network (B-ISDN) used the term to refer to a broad range of bit rates, independent of physical modulation details. In data communications, a 56k modem will transmit a data rate of 56 kilobits per second (kbit/s) over a 4-kilohertz-wide telephone line (narrowband or voiceband). This broad band is often divided into channels or "frequency bins" using passband techniques to allow frequency-division multiplexing instead of sending a higher-quality signal.
In radio, for example, a very narrow band will carry Morse code, a broader band will carry speech, and a still broader band will carry music without losing the high audio frequencies required for realistic sound reproduction. The wider (or broader) the bandwidth of a channel, the greater the data-carrying capacity, given the same channel quality. "Broadband" is a relative term, understood according to its context. In telecommunications, a broadband signalling method is one that handles a wide band of frequencies. Broadband technologies Telecommunications Fundamental aspects of this movement are to suggest that the equitable distribution of broadband is a fundamental human right. In that year, at the World Trade Organization Biannual Conference called “ Financial Solutions to Digital Divide” in Seattle, the term “Meaningful Broadband” was introduced to the world leaders, leading to the activation of a movement to close the digital divide. Since 1999, broadband Internet access has been a factor in public policy. This meaning is only distantly related to its original technical meaning. The term became popularized through the 1990s as a marketing term for Internet access that was faster than dial-up access (dial-up being typically limited to a maximum of 56 kbit/s).
The key difference is that what is typically considered a broadband signal in this sense is a signal that occupies multiple (non-masking, orthogonal) passbands, thus allowing for much higher throughput over a single medium but with additional complexity in the transmitter/receiver circuitry. Whereas a passband signal is also modulated so that it occupies higher frequencies (compared to a baseband signal which is bound to the lowest end of the spectrum, see line coding), it is still occupying a single channel. Later, with the advent of digital telecommunications, the term was mainly used for transmission over multiple channels. Its origin is in physics, acoustics, and radio systems engineering, where it had been used with a meaning similar to " wideband", or in the context of audio noise reduction systems, where it indicated a single-band rather than a multiple-audio-band system design of the compander. Different criteria for "broad" have been applied in different contexts and at different times.
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