From: stephen@sprunk.org   
      
   On 09-Jul-14 14:39, hancock4@bbs.cpcn.com wrote:   
   > On Tuesday, July 8, 2014 8:11:52 PM UTC-4, Stephen Sprunk wrote:   
   >>   
   >>> had a huge cable vault.   
   >>   
   >> Maybe it did originally, but with the advent of SLCs, there's not   
   >> much copper terminating at wiring centers anymore, and the space   
   >> formerly used for cable vaults has been repurposed...   
   >   
   > Would they use SLC to replace an existing in-place underground copper   
   > plant, as in city neighborhoods built in the 1930s-1950s?   
      
   Yep.   
      
   The neighborhood where I grew up was built in the 1970s, all pure copper   
   to the CO a few miles away.  In the late 1990s, the telco ran fiber from   
   the CO to where the copper trunk entered the neighborhood, put in a SLC   
   there, and reterminated all the copper lines onto the SLC.  Then they   
   dug up the old copper trunk and removed it.   
      
   > Do underground copper cables "wear" and need eventual replacement?   
      
   Older ones, yes; they weren't very durable.  Newer materials are   
   virtually impervious to water and rodents, and the wires themselves   
   don't wear out.   
      
   > I heard somewhere that they were pressurized with nitrogen to keep   
   > out moisture.   
      
   Trunk lines are, yes.  In fact, you'll often see shiny nitrogen cans on   
   the side of the road where the telco has noted a loss of pressure but   
   hasn't yet located the leak.   
      
   >>> For whatever reason, another telephone exchange building about a   
   >>> mile > away is apparently abandoned and up for sale:   
   >>   
   >> SLCs also mean you don't need wiring centers all over the place;   
   >> since the trunk is fiber, you can run it much further than a copper   
   >> loop.   
   >   
   > Well, you ntill need space for the physical switch.  The second   
   > bulding served four exchanges, probably with panel.  How much less   
   > floor space does something like a 5 ESS take up compared to a panel   
   > or No. 1 crossbar?   
      
   The guts of a digital switch don't take up much space at all.   
      
   Most of the space is taken up by line cards, and it's the same amount of   
   space for a line card serving a SLC (with 500+ POTS lines on it) as a   
   line card serving one POTS line.  In a sense, the SLC is _part_ of the   
   switch, just not physically located inside the CO.   
      
   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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