pstn

2 definitions found

pstn - Free On-line Dictionary of Computing (26 May 2007) :

  Public Switched Telephone Network
  Plain Old Telephone System
  PSTN
  
     <communications> (PSTN, T.70) The collection of interconnected
     systems operated by the various telephone companies and
     administrations (telcos and PTTs) around the world.  Also
     known as the Plain Old Telephone System (POTS) in contrast to
     xDSL and ISDN (not to mention other forms of PANS).
  
     The PSTN started as human-operated analogue circuit switching
     systems (plugboards), progressed through electromechanical
     switches.  By now this has almost completely been made
     digital, except for the final connection to the subscriber
     (the "last mile"): The signal coming out of the phone set is
     analogue.  It is usually transmitted over a twisted pair cable
      still as an analogue signal.  At the telco office
     this analogue signal is usually digitised, using 8000 samples
     per second and 8 bits per sample, yielding a 64 kb/s data
     stream (DS0).  Several such data streams are usually
     combined into a fatter stream: in the US 24 channels are
     combined into a T1, in Europe 31 DS0 channels are combined
     into an E1 line.  This can later be further combined into
     larger chunks for transmission over high-bandwidth core
     trunks.  At the receiving end the channels are separated, the
     digital signals are converted back to analogue and delivered
     to the received phone.
  
     While all these conversions are inaudible when voice is
     transmitted over the phone lines it can make digital
     communication difficult.  Items of interest include A-law to
     mu-law conversion (and vice versa) on international calls;
     robbed bit signalling in North America (56 kbps <--> 64
     kbps); data compression to save bandwidth on long-haul
     trunks; signal processing such as echo suppression and voice
     signal enhancement such as AT&T TrueVoice.
  
     (2000-07-09)
  

pstn - V.E.R.A. -- Virtual Entity of Relevant Acronyms (June 2006) :

  PSTN
         Public Switched Telephone Network (IN)