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How can i make a LAN Cable Tester?

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New Member
I want to make a LAN cable tester, but i have'nt found any schematics...
Can anyone give me a URL or any schematics?

I want it for RJ-45 and Cat 5 cables.

With abilities to check if the cabel is a Twisted or regular cable and check if all the pairs work. It must have a transmitter and a receiver... For use over longer range.

Thank you!


New Member
well, the tester is a very complicated device.
you can not build a tester that does more then test the continuity of the cable. or maybe you can
you can do somethink like connect the wires from each pair at one end and thest for continuity on the other end. this way you test each pair, but if only one of the wires is broken somewhere you dont know wich one. aso you will not be able to know where the cable interrupted.
you migh then switch the wires and connect them in another way and so this way you can see wich one is interupted.
or you can do this way.
i have an idea. but i cannot post the circuit here, so i will post it in the Electronics ideas.....(the other part of the forum)

Dean Huster

Well-Known Member
Simple or impossible.

I've made one before that used one of the lines as a common connection and then shifted a logical HIGH one-by-one on the seven remaining lines. At the other end, an LED array displayed the results. A good cable was a "light chaser" display while a bad cable had problems with the lighting sequence, some lights not working or some lights working in tandem. However, this is just a simple continuity test, which is probably sufficient in most cases. A good CAT-5 cable tester actually can make a bandwidth test to determine the QUALITY of the installation as well as the correct wiring. Those testers are pricey and I've never seen a DIY version. There was a tester in one issue of the last year of Poptronics magazine before it folded, but I don't think it checked bandwidth.



New Member
wow. it is just like i buid! if you look in Electronic ideas/designs.....you will see that i posted a schematic! but it doesnt need the shield, because in most cases it is not there(in the cable)


New Member
how about if you send electric through one wire, back another, back to the other side, and back, etc.... until all it has gone through all wires..

and then if the connection makes it the entire way, it will light a led, indicating that the cable is good.
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