Posted by Paul Stavf on February 23, 2007, 7:50 pm, in reply to "-48 volts" --Previous Message--
: An instructor at a class posed the question,
: Why do phone companies use the term -48?
: Were did it originate? Were did it start? He
: says he is not actually referring to the -48
: power used in the central office but
: something else. I don't know? Can some one
: help?
:The telephone company does use 48 volts in the CO and the term -48 comes from the fact that telephone offices are "backward" from the somewhat standard electronic nomenclature where the battery negative is grounded to the frame of the equipment and you test for positive. In a CO, you ground the positive side of the battery and test for negative. Some telephone old timers will argue that everybody else is wrong, after all, the telephone standard was set up first.
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