So this reminded me of toys that used 9 volt batteries from the late 70's-80's but they did the job I wanted and passed some tests that I spent. My first job was to trace the thermostat wire into the wall and he did it pretty well. The wire was fed through the studs and I was able to figure out where it crossed so as not to open the wall except where I needed to. I also tested its range on a long extension cord and tested a few RJ45 cords with it. No problem. A few things to note: The metal tip on the receiver isn't the most delicate part. In fact, it reads better at the base of the metal tip. If you can attach alligator clips to two wires in one cable, you'll get a much stronger signal than one (or two) on one wire (two on one wire). was weaker than one). It won't help if you're tracing a specific wire, but if you're tracing a cable it might help. The LED doesn't actually indicate a signal unless you increase the sensitivity. It seems that in order to increase sensitivity, you need to turn up the volume. It gets uncomfortably loud. Plugging in headphones reduces volume while maintaining sensitivity, but the headphones actually get pretty loud too. I think I could plug in dead headphones to turn the sound off completely, THEN use an LED to show signal strength. It would be nice if there was only an optical option. Maybe I'll make a modification. There's no case to keep all the parts in, but the box it came in is great for that. In general I am satisfied. Hope this lasts a while.