network rj45 cable tester circuit

Network RJ45 Cable Tester Circuit

This is a multifunction RJ45 network cable tester. It is the design of the network cable (RJ45) test, and telephone (RJ11). It is cheap and easy to use. It works for network, telephone, cable with RJ45 half “Registered Jack” plug immediately indicate whether a crossover network cable or straight, flashing a yellow or green LED. If something is broken or if you press the button, the tester is in line with the wire test.

How does the network cable tester circuit work?

The top RJ45 connector sends signals to each of its eight legs. The lower RJ45 connector receives signals from the top RJ45 connector created by the wire.

When the red LED above the orange light LED bar shows the pins in the top RJ45 connector sends a test signal, and when the bottom of the red LED illuminates orange LED bar indicates which of the eight dioceses of the bottom RJ45 connector signal receives in this state where the wire is broken or not connected, none of LEDs in the LED bar will light up orange.

If a short circuit between two or more wires, more than an orange LED lights up when the bottom red LED lights. Each time the button is the active output pin.


Related Products:

Wire and Cable | Cable Accessories


RJ45 Cable Tester Specifications

  • For network cable (RJ45) and telephone (RJ11) tests.
  • Similar test can double-twisted cables 1,2,3,4,5,6,7,8 and Ground, meanwhile, can judge wrong connection, short circuit and open circuit.
  • ON / OFF button.
  • With four LED indicator.
  • Composing the master and remote two tests that can take a role in the testing easier.
  • Power by 9V battery.
  • Compact, durable design with a black plastic bag with zipper for storage.
  • Cable RJ45 network and RJ11 phone port


RJ45 Network Cable Tester Circuit Schematic

network rj45 cable tester circuit


Join the conversation!

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  • radcomtech

    (a) Current is about 4-5mA with 1K drops (R4-R7).

    (b) Appears to be similar to the ElectronicsForYou Feb or March 2014, by Bhaskar Pandey. link=

    (c) Far End loop back is not shown in this post but is obviously 1-2, 3-4, 5-6, and 7-8. The astable is likely *faster* in this posted version, as the EFU article above features a C1 with 47 (not 10) uF and is described as “1Hz” for frequency.

    (d) the circuit 555 should/could be modified with a “step/run” switch or a momentary open button to stop the sequence.

    (e) to find a crossed over TIA568 cable would be a bit difficult because the operator does not see the condition of 4017, so an additional modification would be 2K2 resistors in series with LEDs at the 4 outputs of 4017, but with pins directly wired to the first RJ45, and then the same layout at the looped back RJ45 , pins 1-2 / 3-4 / 5-6 and 7-8 connections.

    (f) at some point, a cheaper China Arduino Nano/Mini board could be used and then the two RJ45 jacks could be separated, with the far end wired to resistor dividers and the Ardy reports pin-number-translated-as-the-corresponding-voltage. But 4017 Johnson connected to Astable is so 1990s retro (for ultranerds).

    (g) the explanation in the article is much more coherent than this post.

    • radcomtech

      I correct my (c) comment to read the loopback must be 1-2, 3-6, 4-5 and 7-8,
      but the RJ-11 may be 1-4 and 2-3 (4 wire). I realize there are better ways to wire the loopback or far end.

  • slam

    i just want to know the values of current at pin 7,3,2 and 4.

  • tmac

    why not provide a test for each single wire
    in sequence this can then show what wire is open
    and what is shorted

  • cpalconet

    This is a great grear to have around.


  • cae2100

    for everyone that is curious about the schematic, the design is from another site. here’s the link :

  • rich

    Hmm, where is the circuit for the other end to test the cable??

  • Ben Hutchings

    It’s hard to say exactly what the original poster/writer was trying to do, but looking at the schematic I guess you have a dummy socket the other end with colour pairs shorted together. (green/white to white/green, 6 to 3 for example). Then what the circuit does is check the 4 pairs. If one LED doesn’t light in sequence, you know that there is either of the two wires of the pair are broken.

    It’s OK, but it doesn’t really handle shorts within the cable very well I don’t think?. I want to work on one that does this. I’ll post back if I come up with something.

  • solutionsSF

    The explanation is in very poor English, and I’m not an Electronics Engineer, so I don’t want to guess what the author means. Can anyone translate this into proper English?

    There is mention of an RJ11 jack and two RJ45 jacks, but all I see in the schematic is one RJ45, so I’m lost.

  • Pentaconto

    I do not understand the explanation of this circuit. Is it really correspond with the Circuit Schematic?

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