[time-nuts] [OT] -48 instead of +48 (was:RE: Where does 28V come from?)

[Lamar Owen]

> n3izn at aol.com Wrote:

> Not to steal the thread, but any one know why the telephone company choose to use a negative
> voltage? Where as the positive is referenced to ground? When I was a kid I was told it was 
> because they discovered that the battery terminal would corrode if it was done that way?

Negative 48 was chosen for several reasons, but the primary reason a negative potential was chosen was due to negative voltages causing less galvanic corrosion to outside plant; splices and copper wires outside corrode more quickly when at a positive potential relative to ground.

--
Lamar Owen
Chief Information Officer
Pisgah Astronomical Research Institute
1 PARI Drive
Rosman, NC 28772
828-862-5554
www.pari.edu





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