From: stephen@sprunk.org   
      
   On 08-Jul-14 11:48, Adam H. Kerman wrote:   
   > Stephen Sprunk  wrote:   
   >> SLC = Subscriber Line Concentrator   
   >   
   > I'm confused. What's the name of the device telephone companies used   
   > when they weren't installing sufficient numbers of local loops to   
   > meet a growing number of telephone subscribers, but bumped the   
   > frequency used within the loop so it could be shared by two different   
   > telephone subscribers?   
      
   Frequency multiplexing was analog "pair gain".  Systems were available   
   that supported up to eight POTS lines over a single pair of wires.  At   
   the other end, a matching device was used to turn them back into analog   
   POTS lines, which were connected to the switch as any other.   
      
   With a SLC, the POTS lines were fed into a digital multiplexer; two to   
   four T1 circuits ran to the CO, which were directly connected to the   
   switch; they weren't turned back into analog circuits.   
      
   Most "SLCs" today are actually DLCs; the idea is the same as a SLC, but   
   a variety of line cards are available, e.g. T1 or fiber for the trunk   
   side and POTS, DSL, T1, fiber, etc. for the consumer side.   
      
   S   
      
   --   
   Stephen Sprunk         "God does not play dice."  --Albert Einstein   
   CCIE #3723         "God is an inveterate gambler, and He throws the   
   K5SSS        dice at every possible opportunity." --Stephen Hawking   
      
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