Re: gEDA-user: OT: DC power feed on xDSL circuits

[Steven Michalske <smichalske@xxxxxxxxx>]

On Jan 15, 2010, at 2:48 AM, Peter Clifton wrote:

> On Thu, 2010-01-14 at 03:44 +0000, Michael Sokolov wrote:
>
> >   While SDSL lines in North America are generally unpowered (I've  
> > never
> >   seen one with DC power on it), when someone does put DC power  
> > feed on
> >   a line of this kind (like they do with ISDN for example), they
> >   generally want the user-attached CPE to conduct some DC current  
> > (they
> >   call it sealing or wetting current, supposedly it somehow helps  
> > with
> >   contact corrosion), .....
>
> I'd have thought that passing currents could accelerate contact
> corrosion if they get damp, and there are any dissimilar metals
> involved. (Or help avoid it, depending on the polarity?)
>
> I know that a certain level of current is good for reliable switch
> contacts, so maybe this is also required for connectors, and other  
> types
> of joint such as the IDC ones used in telecoms.
>
> Anyone care to point us to an article or source of authoritative
> information on this topic? I'm afraid I can't even remember the
> mechanism of how it helps relay contacts.


I know that they used to make positive ground systems on telcoms so  
that the Earth is the anode and will deposit ions onto the wires for  
leakage currents.  Instead of having the wire rot away.

Steve


_______________________________________________
geda-user mailing list
geda-user@xxxxxxxxxxxxxx
http://www.seul.org/cgi-bin/mailman/listinfo/geda-user