The trick is to use a split pair. Since the reason that cables use twisted (balanced) pairs is to reduce crosstalk, and your probe is essentially trying to detect a leaking signal that is similar to crosstalk, you need to use 2 wires that are not a pair.

Try putting one toner clip on the white/blue wire and the other clip on the white/brown wire. Do not ground anything.

Let us know how that works.

Another trick, born of desperation, is to examine very carefully, and document, the color, texture, and foot markings on the sheaths. In a large job, unless the installer had access to a billion feet of the same type of wire, chances are that the cables will have come from different manufacturing lots. The foot markings will help narrow down the choices.

If you find one cable out of 24 successfully, and you have a blueprint of the building, by process of elimination, you have a better chance of finding the subsequent cables in a 24-cable group as you find each one. If you are stuck finding the first one, try sending on another. It's often just luck to find the first one. But then, you will have the aural reference and will know what to listen for (in terms of volume, cadence, etc) on the rest of the cables.

Do the testing in a quiet room. Turn off the radio that the plumber is listening to. Shut off as many fluorescent lamps and fans as possible. Chew gum. (I am not making this up. It tends to pop your ears and make them more acute.)

Visualize how the cable is laid up. The wires are not only laid up in pairs, but the pairs are arranged in a big twist, too. The wires you're listening for appear near the jacket only every 6 or 8 inches, periodically. Move the probe slowly along the jacket. The correct cable will have areas of loud signal, and areas of no signal. Be patient.

I have used all different sorts of toners in my 50+ years of doing this. The best one, IMHO, is the original (not the later "improved" one) orange toner made by Aines. (See photo for the exact one I use).

[Linked Image from aines.com] https://www.aines.com/media/aines_tg1.gif




Arthur P. Bloom
"30 years of faithful service...15 years on hold"