In telecommunication, the term baseband has the following meanings:
1. The original band of frequencies produced by a transducer, such as a microphone, telegraph key, or other signal-initiating device, prior to initial modulation.
In transmission systems, the baseband signal is usually used to modulate a carrier. Demodulation re-creates the baseband signal.
Baseband describes the signal state prior to modulation, prior to multiplexing, following demultiplexing, and following demodulation.
Baseband frequencies are usually characterized by being much lower in frequency than the frequencies that result when the baseband signal is used to modulate a carrier or subcarrier.
The composite video signal created by devices such as most newer VCRs, game consoles and DVD players is a commonly used baseband signal. Broadcast or cable television, on the other hand, use a modulated signal to be able to carry many stations through a single aerial or cable.
2. In facsimile, the frequency of a signal equal in bandwidth to that between zero frequency and maximum keying frequency .
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