Klein ET310 How does it work?

[rcbuck]

https://www.kleintools.com/videos/digital-circuit-breaker-finder-gfci-outlet-tester-et310

It actually works. I bought one since I am doing some house rewiring. I plugged it into an outlet inside the house. Went outside to breaker panel and scanned the breakers. When it located the breaker it started flashing and the LED turned red.

When all of the breakers are on they connect to the common bus phase of the incoming electric source. This means they are all connected together on one end of the breaker. There should only be a couple of milliohms contact resistance. Why doesn't it indicate red on all the breakers?

[rcbuck]

Thanks for the reply. The AC injection sounds like what they are doing. It would be fairly easy to generate a 100 or 200 kHz signal with only a couple of components. I may be able to use my spectrum analyzer to pick up the signal to determine the frequency they are using.