If you are willing to spend a little time troubleshooting your own wiring, there is a good chance that this line tester will save you a lot of money on diagnosis and repair. I won't go into how it works, but I will say that I had/had a broken pipe somewhere in the attic. The phone company obviously wanted to charge me for a replacement arm and leg, but I was able to figure out the problem with this diagnostic tool. My particular concern was that one of the cables must have been nicked or damaged during the original construction. and eventually it rusted just enough to create a short circuit. Since all the cables are brought together in a junction box outside the house, the signal was constantly being lost. I know, I know... who still uses a landline? Since we live in the country, we only have DSL. The tester has a short-circuit checking feature, so I could test every outlet in the house until I found the faulty one. I then went back to the junction box and used the scan function to isolate the wires coming from that connector and then just unplugged them from the junction box. The rest of the plugs are no problem, and since we only need one plug for the DSL modem, it didn't matter at all that I unplugged the kitchen plug from the system. I've only used a few of its many features. I'm also planning to run an ethernet cable through the walls and I'll be using that again to make sure I'm getting the connections right and running the right cables in the right places. For the price, it really should be standard in every homeowner's tool box.