Encyclopedia > Signal compression

  Article Content

Signal compression

In telecommunication, the term signal compression has the following meanings:

1. In analog (usually audio) systems, reduction of the dynamic range of a signal by controlling it as a function of the inverse relationship of its instantaneous value relative to a specified reference level.

Note 1: Signal compression is usually expressed in dB.

Note 2: Instantaneous values of the input signal that are low, relative to the reference level, are increased, and those that are high are decreased.

Note 3: Signal compression is usually accomplished by separate devices called "compressors." It is used for many purposes, such as (a) improving signal-to-noise ratios prior to digitizing an analog signal for transmission over a digital carrier system, (b) preventing overload of succeeding elements of a system, or (c) matching the dynamic ranges of two devices.

Note 4: Signal compression (in dB) may be a linear or nonlinear function of the signal level across the frequency band of interest and may be essentially instantaneous or have fixed or variable delay times.

Note 5: Signal compression always introduces distortion, which is usually not objectionable, if the compression is limited to a few dB.

Note 6: The original dynamic range of a compressed signal may be restored by a circuit called an "expander."

2. In facsimile systems, a process in which the number of pels scanned on the original is larger than the number of encoded bits of picture information transmitted.

Source: from Federal Standard 1037C and from MIL-STD-188



All Wikipedia text is available under the terms of the GNU Free Documentation License

 
  Search Encyclopedia

Search over one million articles, find something about almost anything!
 
 
  
  Featured Article
242

... century Decades: 190s 200s 210s 220s 230s - 240s - 250s 260s 270s 280s 290s Years: 237 238 239 240 241 - 242 - 243 244 245 246 247 Events Patriarch Titus[?] ...

 
 
 
This page was created in 31.4 ms