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Compressors usually have controls to set how fast the compressor respondes to changes in input level, known as ''attack'', and how quickly the compressor returns to no gain reduction once the input level is below the threshold, known as ''release''. Also, because the compressor is reducing the gain (or level) of the signal, the ability to add a fixed amount of gain at the output is provided so that an optimum level can be used.
== Companding ==
In [[telecommunication]], this operation and its reverse are together known as '''companding''' (for '''comp'''ressing and ex'''panding''') so called because the [[dynamic range]] of signals is compressed before [[transmission (telecommunications)|transmission]] and is expanded to the original value at the receiver. ▼
▲In [[telecommunication]], this operation and its reverse are together known as '''companding''' (for '''comp'''ressing and ex'''panding''', also called '''compansion''') so called because the [[dynamic range]] of signals is compressed before [[transmission (telecommunications)|transmission]] and is expanded to the original value at the receiver.
This is typically carried out in analog systems by using a [[voltage controlled amplifier]] which has its gain reduced as the power of the input signal increases.
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The use of companding allows signals with a large dynamic range to be transmitted over facilities that have a smaller dynamic range capability. Companding reduces the [[noise]] and [[crosstalk]] levels at the receiver.
== See also ==
* [[Dolby system]]
* [[Mu-law_algorithm|mu-law]]
* [[A-law_algorithm|A-law]]
* [[Squelch]]
* [[Automatic gain control]]
== External links ==
* [http://www.audio-technica.com/using/wireless/advanced/compand.html A description of companding in wireless microphones]
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