[rescue] 48 VDC v -48 VDC...jeez!

[Kris Kirby]

On Fri, 19 Jul 2002, Leslie Connally wrote:
> Can I assume NOT everyone in telecom uses -48vdc? Is most telecom
> -48vdc ?

Most telco COs run on *massive* installations of 48V batteries. They just
happen to like to use the positive as the common side.

> which is f((*&g "supply" and which is "return" ???

> >Netra t1 100 DC
> >o -48VDC/-60VDC Supply (pin 1) (12 AWG)
> >o Ground connection to power supply (pin 2) (12 AWG)
> >o -48VDC/-60VDC Return (pin 3) (12 AWG)

Supply would be the negative lead in this case. Return would be the
positive lead, since -48VDC implies that the polarites are reversed.

I had trouble wrapping my head around this one too, years ago. The next
worse one for me was active-low logic.

You could always ship me one and I could find out and get back to you. ;-)

--
Kris Kirby, KE4AHR  <kris at nospam.catonic.net>  TGIFreeBSD IM: 'KrisBSD'
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