Editing Pulse-amplitude modulation (section)

==Types==
There are two types of pulse amplitude modulation:
* In ''single polarity PAM'', a suitable fixed [[DC bias]] is added to the signal to ensure that all the pulses are positive. 
* In ''double polarity PAM'', the pulses are both positive and negative.

Pulse-amplitude modulation is widely used in [[modulating signal]] transmission of digital data, with non-[[baseband]] applications having been largely replaced by [[pulse-code modulation]], and, more recently, by [[pulse-position modulation]].

The number of possible pulse amplitudes in analog PAM is theoretically infinite. Digital PAM reduces the number of pulse amplitudes to some power of two. For example, in 4-level PAM there are <math>2^2</math> possible discrete pulse amplitudes; in 8-level PAM there are <math>2^3</math> possible discrete pulse amplitudes; and in 16-level PAM there are <math>2^4</math> possible discrete pulse amplitudes.