Yes, I appreciate that now. My homebrew tester was good enough...I would have had to make the same mistake both ends for it not to show as a fault. I can see a cowboy installer doing that, though!
Yes, my introduction to this was some years ago when I inherited a network which had been recenty 'upgraded' from co-ax to utp. It seemed to work OK when all the devices were 10Mbit, but the 'new' 100Mbit devices were falling over.
The installation had been done by a well-meaning but clueless electronics maintenance guy who had no knowledge about ethernet wiring.
A few days of re-punching-down had everything working.
Bob Eager wibbled on Monday 09 August 2010 22:03
I agree. It's very easy to make a mistake with lack of light in a tight space even for a pro. But you'd be very unlucky to counter that mistake with another random error on the other end - melted my head trying to work it out but I suspect it's worse than the square, so even if you made a mistake on 1 in 20 connections, I suspect (real statistians please step forward) it would be somewhat less than 1 in 400 of making a mistake a DC tester passed as valid.
So the pub quiz question for tonight is, with the given scenario and a probabality of swapping a pair of wires being 1 in X, what's the actual probability of doing that both ends and getting the correct buzz through pip to pin?
Yes I have a commercial pair of units that does the same job, albeit the switching stepping through the pairs automatically.
But take my word for it, this kind of tester will diagnose straight, crossover, short circuit and open circuit pairs, but it will be unaware of split pairs! After all, how could it? The tester will see the copper conductors forming circuits exactly as expected, the only difference is what it sees as a pair of conductors, are not mutually twisted together.
ected, the only difference is what it sees as a pair of
Yup guys, I now got the difference between split pairs and any other wiring anomaly ;-)
Backing what Ron said the importance of getting it right, from another forum:
sues when they installed early electronic fluorescent ballasts. Switching c= omputer power supplies caused similar problems. T1's happily ran alongside = phone wires for decades until DSL came along.
Today, we're seeing a profusion of powerline communication schemes, each with it's own set of interference issues.
In message , "dennis@home" writes
It will show them if the installer hasn't made the same mistake at each end but if they have then you're sunk...
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