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TOPIC: Simple Circuit Tests Twisted-Pair Cables - Try 2

Re: Simple Circuit Tests Twisted-Pair Cables - Try 2 6 years 6 months ago #16404

  • Jon Chandler
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An EDN Design Idea - Originally published in the May 29, 1986, issue of EDN



Mark D Braunstein, Contel Information Systems, Fairfax, VA; Edited by Paul Rako and Fran Granville - January 19, 2012

Using the system shown in below, you can quickly test a cable containing twisted-wire pairs and detect open or reversed pairs, shorted pairs, and shorts between unrelated pairs. The tester consists of an active test set that plugs into one end of the cable, and a passive terminator that plugs into the other end. (An RS-449 cable is used as an example.)


Simple Circuit Tests Twisted-Pair Cables

This circuit should prove useful to anyone using multi-pair cables.  The idea would work well for an RJ-45 network cable tester.


 
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Re: Simple Circuit Tests Twisted-Pair Cables - Try 2 6 years 6 months ago #12835

  • Jon Chandler
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Sorry if you've noticed this article appear and disappear several times. My quick copy and paste job turned out to be more troublesome than expected.

Happy new year all!

Re: Simple Circuit Tests Twisted-Pair Cables - Try 2 6 years 6 months ago #12836

  • Jon Chandler
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Looking at this in a little more detail, it will work well to detect opens, shorts and pairs connected backwards are one end. It will not detected pairs connected out of order...say pair 1 at one end connects to pair 4 at the other. Therefore, it's not effective to detect RJ-45 cross-over cables...

Maybe we can do better?

Re: Simple Circuit Tests Twisted-Pair Cables - Try 2 6 years 6 months ago #12874

  • majenko
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Why not use the bi-directional red/green LEDs (two pin, connected in opposite directions, you know the ones) for the terminator end? Green = good, off = open / short, and Red = connected backwards. Better diagnostics then
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