Editing Signal (section)

====Analog signal====
{{main|Analog signal}}

An analog signal  is any [[continuous signal]] for which the time-varying feature of the signal is a representation of some other time varying quantity, i.e., ''analogous'' to another time varying signal.   For example, in an analog [[audio signal]], the instantaneous [[voltage]] of the signal varies continuously with the [[sound pressure]]. It differs from a [[Digital signal (signal processing)|digital signal]], in which the continuous quantity is a representation of a sequence of [[discrete value]]s which can only take on one of a finite number of values.<ref>{{Cite web|url=https://www.st-andrews.ac.uk/~www_pa/Scots_Guide/info/signals/digital/digital.htm|title=Digital signals|website=www.st-andrews.ac.uk|access-date=2017-12-17|url-status=live|archive-url=https://web.archive.org/web/20170302055200/http://www.st-andrews.ac.uk/~www_pa/Scots_Guide/info/signals/digital/digital.htm|archive-date=2017-03-02}}</ref><ref>{{Cite web|url=https://learn.sparkfun.com/tutorials/analog-vs-digital/digital-signals|title=Analog vs. Digital - learn.sparkfun.com|website=learn.sparkfun.com|language=en|access-date=2017-12-17|url-status=live|archive-url=https://web.archive.org/web/20170705100418/https://learn.sparkfun.com/tutorials/analog-vs-digital/digital-signals|archive-date=2017-07-05}}</ref>

The term ''analog signal'' usually refers to [[electrical signal]]s; however, analog signals may use other mediums such as [[Classical mechanics|mechanical]], [[pneumatic]] or [[hydraulic]]. An analog signal uses some property of the medium to convey the signal's information. For example, an [[aneroid barometer]] uses rotary position as the signal to convey pressure information.  In an electrical signal, the [[voltage]], [[Electric current|current]], or [[frequency]] of the signal may be varied to represent the information.
   
Any information may be conveyed by an analog signal; often such a signal is a measured response to changes in physical phenomena, such as [[sound]], [[light]], [[temperature]], position, or [[pressure]].  The physical variable is converted to an analog signal by a [[transducer]].   For example, in sound recording, fluctuations in air pressure (that is to say, [[sound]]) strike the diaphragm of a [[microphone]] which induces corresponding electrical fluctuations.  The voltage or the current is said to be an ''analog'' of the sound.