On Fri, 16 Nov 2007 16:58:31 -0000, steveybar
wrote:
>
>Ivor Jones wrote in message
>news:5q5lrnFu6qbgU1@mid.individual.net...
>> wrote in message
>> news:8b8a3b8a-e02d-404a-b16a-d231440406df@e25g2000prg.googlegroups.com
>> : : why telephone offices have -48V sypply ?
>>
>> Its 50V actually, to power the exchange (not CO were British here)
>> equipment, why do you ask..?
>>
>> Ivor
>>
>
>Yes, Ive also always wondered why -50v dc, why not -25v or -75v or -100v or
>.....?
No idea, something historical and probably thought of in the days
before there was even a Post Office Electrical Engineers Journal
>And whilst we are at it, why is it a -ve value (-50v), and not a +ve value
>(+50v) ?
Because the +ve is earthed
Now ask why.......
:)
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Posted: 2007-11-16 18:16:33
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