[lug] ethernet cable tester

[Carl.Wagner at Level3.com]

I would bet that it has 2 jacks and you plug both ends of the cable in to
check
for miswires.  Otherwise you just about have to have at least a passive device
on the
other end.

Carl.

"J. Wayde Allen" wrote:
> 
> On Mon, 18 Dec 2000, Alan Robertson wrote:
> 
> > The 46060 Sure Signal tester can be found in this catalog:
> >       http://www.greenlee.textron.com/download/archive/ticat.pdf
> > on page 61.  It is definitely yellow, too ;-)
> >
> > I don't quite understand how you can test a cable just from one end.  How do
> > you use this gadget?  [or how does it work?]
> 
> I don't know how this particular gizmo works exactly, but the spec.'s in
> the catalog says it checks primarily for short circuits and
> miswires.  The short circuit is easy, just check that there is no
> connectivity between any two wires in the cable bundle.
> 
> The miswiring is a bit unclear.  I'd think that would depend on the
> specifics of how a properly wired cable would be terminated.  That is info
> I don't have.  However, some obvious miswiring would create short circuits
> between the wires in the cable bundle or complete opens where there should
> be a nominal resistance due to the terminating electronics.  Another
> possibility would be to test for any supply or bias voltages that should
> exist on a properly wired and connected line.  For example, a properly
> wired phone line will have nominally 50 volts DC between the two wires.
> This doesn't look like a particularly sophisticated gizmo, so I'd be a bit
> surprised if it does much more than this.
> 
> A more sophisticated machine such as a time domain reflectometer could
> send an RF pulse down the line and see how the pulse propagates.  Changes
> in line impedance would cause reflections in the line.  Measuring the time
> delay of these reflections from the initiation of the pulse allows you to
> compute the distance down the cable to the impedance change as well as
> allowing you to identify to some extent the cause of the reflection.  For
> example, an open circuit has a reflection coefficient of 1 while a short
> circuit's reflection coefficient is -1.
> 
> Just some possible ways that you could test a cable from just one end.
> 
> - Wayde
>   (wallen at lug.boulder.co.us)
> 
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