Editing Multiplexing (section)

===Frequency-division multiplexing===
[[File:Frequenzmultiplex001.svg|right|thumb|400px|Frequency-division multiplexing (FDM): The spectrum of each input signal is shifted to a distinct frequency range.]]
[[Frequency-division multiplexing]] (FDM) is inherently an analog technology. FDM achieves the combining of several signals into one medium by sending signals in several distinct frequency ranges over a single medium. '''In FDM the signals are electrical signals.'''
One of the most common applications for FDM is traditional radio and television broadcasting from terrestrial, mobile or satellite stations, or cable television. Only one cable reaches a customer's residential area, but the service provider can send multiple television channels or signals simultaneously over that cable to all subscribers without interference. Receivers must tune to the appropriate frequency (channel) to access the desired signal.<ref name = "Bates">{{citation | title = Voice and Data Communications | first1 = Regis J | first2 = Marcus | last1= Bates| last2 = Bates | year = 2007 | publisher = McGraw-Hill Irwin | isbn = 9780072257328}}</ref>

[[Image:WDM operating principle.svg|400px|thumb|One stream, one color, light waves, in WDM]]
A variant technology, called [[wavelength-division multiplexing]] (WDM) is used in [[optical communication]]s.