From: stephen@sprunk.org   
      
   On 25-Jun-14 09:25, hancock4@bbs.cpcn.com wrote:   
   > On Tuesday, June 24, 2014 12:42:33 PM UTC-4, Stephen Sprunk wrote:   
   >   
   >> 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.   
   >   
   > ...   
   > I believe the basic features you mention were available on early   
   > generation electronic switches, definitely by the early 1970s.   
   > Transfer and 3-way calling didn't need any special code; the person   
   > merely flashed the hookswitch, got a second dial tone, and dialed the   
   > next number.   
      
   That's why I said "or using hookflash".   
      
   > In 1976 Bell developed new custom features for its Dimension PBX,   
   > these additional features required special electronic telephone sets.   
   > I'm not sure if they were "digital" in the sense you described it.   
      
   I just scanned the first page of the PDF, but it looks like their   
   "electronic" sets are what we now call "digital" phones.   
      
   > More sophisticated features were available, but did require dialing a   
   > special code.  As you said, many users did not know how to use them   
   > unless it was a routine part of their job.  Heck, today many people   
   > don't even know how to transfer a call.   
      
   It's a lot easier to teach them "press the Transfer key, dial the   
   number, and hang up" than to teach them the hookflash method (where   
   available) on analog phones, which is easily confused with the hookflash   
   sequence for 3-way calling (where available).   
      
   Also, if you tried using either on an analog system that _didn't_ have   
   either of those features, you would lose the call; whereas if it had one   
   but not the other, you could get the wrong result.  A digital system's   
   explicit transfer key means you know it's safe to use and that you will   
   get what you wanted.   
      
   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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