Introduction: Pocket Cable Tracer

Picture of Pocket Cable Tracer

Get wired with gigabit speed. Trace your network cables with this tiny tester.

Fast, cheap, and easy to build. No soldering needed.

You need a wired home network for gigabit speed.

This little gadget will help you find both ends of your network wiring when you have a bundle of wires coming together in the basement.

It sends a pulsed 90+ volt DC signal down your CAT5 and other wires so it can give you a startling, but harmless shock if you touch the leads.

Step 1: Parts

Picture of Parts

Your local discount or dollar store probably carries this battery-powered alarm for about a buck.

You will also need a package of alligator clips, also about a dollar.

Get a neon voltage tester for a dollar while you are there.

Step 2: Internal Mods

Picture of Internal Mods
  • Slide off the battery door.
  • Remove the batteries so you don't get shocked while clipping the leads.
  • Remove the Philips screw which holds the case together.
  • Cut the wires leading to the flat piezo buzzer disk.
  • You will be using these wires as your test leads in the next step, so clip them right at the disk.

Step 3: Open Notch

Picture of Open Notch

Use a knife to open up the notch in the edge of the plastic case.

Feed the two loose wires around the tab out through the widened notch.

Put the circuit board back in place.

Close the case and screw it back together.

Step 4: Add Alligator Clips

Picture of Add Alligator Clips

The alligator clips should have a screw terminal, or a crimp fastener.

Attach the bare metal ends of the two short wires from the circuit board to the alligator clips.

Step 5: Trace Time!

Picture of Trace Time!

First test the tracer by connecting the alligator clips right to the leads of your neon voltage tester.

The neon bulb should glow brightly. Remember, if it can light a neon glow bulb, it can give you a harmless, electric sting if you grab both leads. Now you are ready to go.

I like to unscrew the wall plate for network, telephone, or coaxial cables.

Then I attach the alligator clips directly to stripped ends of the pair (usually blue and white for Ethernet) I want to trace.

Another way, shown here, is to clip the to the red and green wires of an RJ11 standard telephone plug.

An RJ11 can be used with either phone or RJ45 Ethernet jacks for testing.

Step 6: Find Your Wires

Picture of Find Your Wires
At the other end you have two ways to find the pair of wires with the signal on them.

Contact Method
  • Strip half an inch of insulation from the blue and white pair. Now test with a dollar store neon volt indicator

Non-Contact Method
  • Untwist the pairs as shown. Now any pocket radio will pick up the beeping tone.


DanR192 made it! (author)2017-06-06

Great project. Definitely works (if the other end of the cable is unplugged, which unfortunately for me wasn't the case) in my testing. I used a different donor item (see picture) - a "personal panic alarm". Same procedure, with the added benefit of a flashing light so you know when it is on.

DashB (author)2015-11-05

for how much is

Pocket Cable Tracer

by iectyx3c

dasheno (author)2015-06-22

I made it. This was really cool to see the signal up on my O-scope.

My only question is I wanted to make this a toy shocker as well but the two leads when touched didn't do anything. (maybe it was really weak?).

Also without the Piezo in there it was still slightly making the ghostly noise (SPOOKY haha)

Any ideas why this isn't giving a slight shock?

I measured above 300 volts for the spikes

AshleyG3 (author)2015-03-16

Ok, all good if you know or have an idea where both ends are, what if you only have one end and you would like to trace the wire through the walls etc to get an idea of where the wire runs the other end come out...

billgeo (author)2013-12-21

It must be an AM band radio, right? What's the frequency of the audio? How long is the wire you tested?

internethotspot (author)2011-03-29

Anyway to trace single wire? Anyway to use sound instead of electricity?

This could theoretically work by transmitting an audible-frequency (like 10kHz) electrical signal from the tone generator, and hooking up a speaker to the inductive amplifier, so the signal will get picked up and converted to a 10kHz audio tone. I'm not sure of the specifics of how to do this, but the principle should work.

Also, a simple band-pass filter will help tune out other electrical noise(see my diagram) -- the values specified should create a very narrow range of 9.6kHz-10.6kHz if I've done my calculations right.

(BTW, I chose values from parts I could order from -- one of my favorite online parts stores that I prefer over the "big guys" ;) )

lperkins (author)internethotspot2011-12-04

Single-wire tracers work by using the wire in question as a radio antenna and an inductive amplifier to detect the signal. So far as I know there's not feasible way to transmit sound through wire without using electricity.

Wo0kiE (author)2010-12-02

this is quite possibly the smartest idea I have seen for the alternative use of a magnetic alarm...


CrouchingFather (author)2010-09-12

Why not use the flat piezo buzzer disk with clips on the other end?

alaskanbychoice (author)2010-01-23

Why not just use a water alert, just twist two wires together at one end then test the other end by touching the wires to the water alert at the other end. Or attach the water alert wires to wires at one end, then go touch wire together at the other end till you here it beep, then you know which wires are which.

Whatnot (author)2009-07-22

You might have explained the theory of operation first. I'll do it for you: You remove the reed relay (the magnetic switch) of a magnetic alarm doohickey so it always beeps when it's on, then remove the piezo disk (the speaker) and instead of that attach alligator clamps to the wires, then when you attach those to an unconnected telephone/network/coax cable on one end you can 'listen' on the other side if you get the signal and on which cable you get that signal if there are many.

MrPotatoHead (author)Whatnot2009-11-09

This is exactly what I though also. Easier to test also, plug it on one side and short the other end. If it doesn't right you have the wrong wire(s).

coilsinamotor (author)2009-08-02

cool but still room for improvement

ooda55 (author)2009-07-23

this is simalar to the method used to trace cables at BT (british telecom) to check you have the RIGHT pair (not one correct wire and another wire of the same colour that is disconnected) you can touch both the wires together to short it out this should stop the beeping indicating you have the correct pair

iectyx3c (author)ooda552009-07-23

Great tip, thanks!

agis68 (author)2009-07-23

that's clever one!

fwjs28 (author)2009-07-20

hmm, interesting.. i saw something simmilar to this using a wireless dog fence and an am/fm radio ...i think this i s the same principal

iectyx3c (author)fwjs282009-07-22

Yes I have seen the electric dog fence people use a radio. This is a little different because the twisted pairs in the network cable pretty much prevent it from acting like a broadcast antenna. That's why in the last step you have to either test the stripped ends, or untwist an inch or so of the wires so a radio can pick up the signal.

fwjs28 (author)iectyx3c2009-07-22

ahh, i see...

fwjs28 (author)2009-07-20

hmm, i see...i'll have to remember this next time i do some (re-)wiring around the house..

janet_aj27 (author)2009-07-18

For a Good TechHead, making stuff is much more creative than buying off the shelf, it gives you a chance to customize and set you apart from the rest.

iectyx3c (author)janet_aj272009-07-18

You are so right. Modding stuff to make it your own is a great way to learn. I find some of my best gear to mod at discount or dollar stores. I study how it works and try to think of new uses for it, or for the parts. For instance the piezo disk in this burglar alarm has all sorts of fun uses.

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