I have used it in a hospital that has hundreds of phones, and I can say that it is very reliable. I could find the line I wanted from the telephone socket using the tester, and it worked perfectly. As soon as I get the chance, I will buy it for myself.

P.S. I would like to make a note. Many complain that their tester does not detect correctly or that it causes confusion (any tester). You are using the tester incorrectly, which is designed for telephone cables and not for electricity. Many of you connect it to phase-neutral to find the line, and even if there is no electricity, with so many branches, it is logical for the buzzer to sound randomly. There are other instruments for testing electricity.