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.
Note 1: In
transmission systems, the baseband signal is usually used to modulate a
carrier.
Note 2: Demodulation re-creates the baseband signal.
Note 3: Baseband describes the signal state prior to modulation, prior to
multiplexing, following
demultiplexing, and following demodulation. (
188 )
Note 4: 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.
2. In
facsimile, the frequency of a signal equal in
bandwidth to that between zero frequency and
maximum keying frequency. (
188 )
