From: gtaylor@tnetconsulting.net   
      
   On 1/25/20 11:37 AM, gfretwell@aol.com wrote:   
   > It is really just arbitrarily deciding which side of the 48v you are   
   > going to ground or use as a chassis common. From the aspect of how   
   > it works, you only need to respect the polarity of attached equipment   
   > if it cares.   
      
   Okay.  That's what I'm starting to understand.  Thank you for confirming.   
      
   > The best reason I have heard to do it has to do with minimizing   
   > electrolysis but simply based on the number of negative ground systems   
   > you see, it must be a minimal effect.   
      
   I don't know how minimal the effect really is.   
      
   I suspect in an optimal circuit, the effect is minimal.  But I further   
   suspect that a sub-optimal circuit the effect is considerably larger.   
   Consider wiring with imperfect insulation buried and wet, thus forming   
   an alternate path back to the source.  If this happens on the negative   
   side, the electrolysis effect could be considerably greater than if it   
   happens on the positive side.   
      
   > You are right, POTS telco systems are 48v positive ground. Somebody   
   > over 100 years ago made that decision.   
      
   I think I read where POTS telco systems started with negative ground and   
   then switched to positive ground to combat corrosion.   
      
      
      
   --   
   Grant. . . .   
   unix || die   
      
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