How to Make a Homemade Network Cable Tester

Written by eli laurens
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How to Make a Homemade Network Cable Tester
Typical Commercial Network Tester (

Network cable testers are basically a battery and several lights, with the network cable itself providing the current path. If the cable is good, the bulbs will illuminate. Making one of these at home can take the average person about fifteen minutes.

Skill level:

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Things you need

  • Four feet of working network cable (with caps)
  • Network wall jack or female socket
  • Wire strippers
  • One battery (several chained AAs or one 9 volt)
  • Light bulbs with wires attached to their leads
  • Electrical tape

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    Making a Homemade Network Tester

  1. 1

    Cut the working network cable so that there is more than a foot of cable to each capped end. The clear adaptor caps will allow it to be plugged into a networking socket, and they can be for CAT-3, CAT-5 or any variant.

  2. 2

    Strip the wires on both of the working network cable's cut ends, and separate the wires by colour. There should be two types for each colour, one solid and one striped. These will serve as the positive and negative leads for the light bulbs.

  3. 3

    Connect the ends of one stripped cable to each of the light bulbs, using the solid wire for the positive terminal. There should be half as many bulbs connected to the cable than wires in the cable; if there are eight strands in the cable, there should be four lights. If the desired tester is to be used on capped network cable itself, then the female wall plug adaptor can be connected to the stripped wires. It has screws in the back that will accommodate eight wires, or four paired connections. Once splicing is complete, wrap all connections with a liberal amount of electrical tape, to prevent them touching each other or grounding out.

  4. 4

    Connect the solid coloured wires of the remaining stripped length of cable to the battery's positive terminal, and the striped wires to the negative terminal.

  5. 5

    If using the female jacks, connect the wires from a second female adaptor to the positive and negative terminals on the battery, as described above.

  6. 6

    When the cable with lights is plugged into a network jack (or has its jack plugged with a cable), and the battery's adaptor is plugged into the terminating lead of that jack or cable, the lights will illuminate for each pair of wires in the cable. If one or more lights do not light up, then the cable could be bad.

Tips and warnings

  • Be sure that all connections are secure, use a soldering iron if desired.
  • Do not plug the tester into a wall jack until it is fully assembled.

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