Hi Richard,
On Saturday 07 January 2006 22:06, Richard King wrote:
> Hi Derrick,
>
> The auto-sense business just deals with accepting straight-thru or
> cross-over cables - in the old days, you had to use the correct
> cable. Nowadays, routers don't care. I'm not yet convinced of Carl's
> "probable" solution, not over 5 meters of wire! I shall have to make
> another cable like that, just to test!
If you think about it, irrespective of the pairs, a straight cable has
pin one at one end connected to pin one at the other. Two to two and
so on.
As far a testing goes, the tester should be able to distinguish between
a correctly wired straight and both types of cross over cable. Pure DC
metrics can determine this.!
In the case of my tester, I get four green lights for a correctly wired
straight cable. Two reds and two greens for a cross over one. An O/C
pair will cause one or more led to remain un-lit.
> If I decide to make my own tester, it will have to detect the kind of
> problem I've been talking about. Some kind of frequency sweep
> arrangement, to look for maximum cross-talk in each pair?
If you want to qualify a cable in order to confirm acceptance, then you
need a vector analyser.!! This will not only provide impedance
measurement, but will allow crosstalk between pairs and between wires
in a pair to be measured across a specified range of frequencies.
Ideally at twice the maximum working frequency. Also the loss along
the line can be determined as well.
Whilst I have the equipment to do qualification testing, I wouldn't
dream of attempting to build it !!!
> Just reading the manual: it says it checks TIA-568A&B cables - no, it
> doesn't!
>
>
> Regards,
>
> Richard.be
> Sent: Saturday, January 07, 2006 4:47 PM
> Subject: Re: Cat 5 cable
>
> > Hi Richard,
>
> <snip>
>
> > The router is able to "Auto sense" the cable wiring and swap over
> > the connections for itself.
> >
> >> I guess I'll give back the tester - another shop has them for $35!
> >
> > Why not just make your own tester ? Two sockets, four LED's, four
> > resistors and a PP3 battery. Plus a plastic box to put it all in
> > !! Mine cost less than a couple of quid and about an hour to make.
> > The wife hasn't discovered the missing watch case yet ! Its been a
> > fair while though !!
> >
> >> Regards,
> >>
> >> Richard.be
--
Best Regards:
Derrick.
Pontefract Linux Users Group.
plug at play-net.co.uk
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