Finding a lost cable

[Osprey]

I have 'lost' a length of CAT5 cable, one end is where it should be, but the other it does not appear where it should in the comms cupboard. My assumption is that the company I had in to fit the fitted furniture in the study have trapped this behind one of the built in units at some point.

I don't want to rip out all the units - not an option. I could cut an access hole in the back or base of one of them - where for example it would be hidden when drawers are in place.

But it would help if I could get a good idea of where the cable is (or where it's held up) ... I have tried using a tone-tester down the cable, but that won't work as soon as tone lost as soon as cable disappears into the wall. Anybody any suggestions of something I can inject 'into' the cable, and how I can trace it ?

( The cable is a foil screened CAT5e )

Otherwise I will have to run in a new cable ... and this would be so damn annoying having built the rest in.

[Me]

silly non serious answer but could work..... get some electrical cleaning solvent and colour it with food dye and 'inject' down the cable and then look for the pool of colour leaking out or smell for it!

could work!

[dmc]

If you are only using it for 100Mb and you have another one that has the same run you could always run two down the same bit of stp. Of course, the network purist will be screaming at me for suggesting that (and if its

1000Mb or more exotic then it's a non-starter anyway).

Got me out of a lot of work once - make sure you label it well though!

Darren

[Tony Williams]

In article , Osprey wrote: [snip]

Perhaps a nasty spikey/square wave, injected into the cable between screen and Earth. The spikey/square waveform gives a broadband noise source. Then look for the far end of the 'aerial' with a transistor AM receiver.

Perhaps generate the nasty spikes with an old fashioned buzzer, either bought or made up with a relay and dc supply.

ASCII art follows, view with fixed-width font and no automatic wrapping.

DC+ ----+---------+ | | _|_ )| Diode /_\ )| Relay Coil | )| | )| | | +---------+----------->Cat5e Screen | + / Relay, normally closed contact, + (opens when relay is energised). | DC- --------------+---+ __|__Earth /////

There will be a bigger signal without the diode, but the relay contacts will be ruined without it.

[Roger Mills]

How about connecting one conductor to mains live, and look for it with a mains cable detector?

[Ian_m]

Fluke make a range of network cable testers, we had one in my last place (about £350) that could identify breaks in cable and other features. Very handy. Used for the following:-

- Identified a break 30m along cable when builders cut through cable whilst building a partition wall.

- Identified that there was 50m of cable hidden in roof for a cable that went one partition wall (giant coil left in roof).

- Identified when one of the bosses modified his PC setup using 75 Ohm coax rather than 50 Ohm coax !!

[Duracell Bunny]

Use the toner - short all 8 wires together, one toner contact on those, other contact on the foil - it works for coax too of course. Set the tone to maximum sensitivity too, of course.

[Osprey]

It didn't work on CT100 .... I have around 35 of these, and the Buzz tester certainly could not detect any of then.

[Osprey]

I'll ask in work maybe somebody has one.

[Robert Laws]

Would it help to earth the central conductors also, assuming the tone generator is floating? Then the applied volts will be on the outside.

Ribert

[tony sayer]

Maplin do a simple and cheap line tracer for such wiring mainly used to identify phone pairs but it works very well with CAT 5 having used it for just this sort of problem and very successful it has been too!...

[Tony Williams]

I've just done the experiment. Connected a reel of pvc insulated stranded wire to a square wave signal generator, running at 50Hz, 10V peak-peak. The 0v was connected to mains earth. Threw the reel down the stairs to get a 20-odd foot length.

The signal from the wire saturated the medium wave of the transistor radio, a raspy buzz, loudest at the lowest frequency. The signal strength could be altered by turning the receiver in relation to the wire, and at the highest sensitivity point the buzz could be heard from about 18" inwards. Turning the receiver away as it got closer allowed about a 2" detection accuracy.

[Duracell Bunny]

Try another toner - this works well with my Fluke unit, and my old Microtest set. Won't work with cheapies typically.

[Osprey]

looks like a job for me this weekend ... along with usual puzzled looks from SWMBO

[Jim Michaels]

If you connect the tone generator between the shield/screen and earth, you should be able to trace it even in a wall behind a cabinet.

Remove SPAMX from email address

[Osprey]

I did ... and it doesn't :-( you can't find the cable once it's in the wall.

I'll probably try making the mains version mentioned in thread.