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

[Peter Clifton <pcjc2@xxxxxxxxx>]

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.

Best regards,

Peter Clifton



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