From: stephen@sprunk.org   
      
   On 24-Jun-14 10:00, hancock4@bbs.cpcn.com wrote:   
   > On Monday, June 23, 2014 3:20:35 PM UTC-4, Stephen Sprunk wrote:   
   >> "Digital" PBX lines typically use POTS-style analog on the first   
   >> pair for the voice path plus digital signaling on the second pair.   
   >> This enables numerous features not available with analog   
   >> signaling.   
   >   
   > Could you elaborate on the extra features available with digital   
   > signalling?   
      
   It's hard to provide a precise list since it varied by vendor.  Some   
   analog PBXes did have some advanced features, such as forwarding,   
   transfer or 3-way calling, accessible by dialing special feature codes   
   or using hookflash--and many of those eventually appeared on home phone   
   lines as well, as premium options.   
      
   OTOH, a digital set would give you a button for forwarding, a button for   
   transfer, a button for call park, etc. so users didn't have to remember   
   all those weird codes--and that made those advanced features accessible   
   to casual users.  That was, perhaps, the real advance of digital PBX   
   sets, not the feature set per se; many of the features were probably   
   available on analog PBX sets but few users (other than the PBX operator,   
   maybe) had any clue how to use them.   
      
   > Would you know when this became widely available?  I think some   
   > people have had it for many years.   
      
   I know I saw them in the early 1990s, but I probably wouldn't have   
   recognized them any earlier than that--and I wasn't exposed to many   
   office environments before then anyway.   
      
   But, as a general rule, if it has roughly the same buttons as and looks   
   like a phone in your house, it's probably an analog PBX phone, whereas   
   if it has lots of buttons and looks weird, it's probably a digital or   
   VoIP PBX phone.   
      
   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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