On 27 Apr 99, at 14:36, Don Riggs wrote:
> Those current-carrying wires are enclosed in close proximity in a cord, and
> the opposite direction of current flow cancels the external magnetic field
> to a great extent. Example: A clamp-on type meter cannot reliably measure
> the current through a cord; the two current- carrying conductors must be
> separated and the clamp placed over one of them to measure current.
>
> <snip>
>
> That does not seem to apply to digital signal systems to any great degree. I
> have seen installations where hundreds of feet of Cat-5 cabling for 10 baseT
> and 10/100 systems were in close proximity, with no apparent ill effects.
Reacll that Cat-5 is unshielded *twisted pair*. Exactly the same
phenomenon limits external magnetic field from these cables as in the power
cords alluded to above.
David G
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