Editing Passband (section)

== Digital transmission ==
There are two main categories of [[digital communication]] transmission methods: [[baseband]] and passband.

* In baseband transmission, [[line coding]] is utilized, resulting in a pulse train or digital [[pulse amplitude modulated]] (PAM) signal. This is typically used over non-filtered wires such as fiber optical cables and short-range copper links, for example: [[ITU-T V.29|V.29]] ([[EIA/TIA-232]]), [[ITU-T V.35|V.35]], [[IEEE 802.3]], [[SONET/SDH]].
* In passband transmission, [[digital modulation]] methods are employed so that only a limited frequency range is used in some bandpass filtered channel. Passband transmission is typically utilized in wireless communication and in bandpass filtered channels such as [[DSL filter|POTS]] lines. It also allows for [[frequency-division multiplexing]]. The digital bitstream is converted first into an equivalent baseband signal, and then to a [[radio frequency|RF]] signal. On the receiver side a [[demodulator]] is used to detect the signal and reverse the modulation process. A combined equipment for modulation and demodulation is called a [[modem]].