I purchased this device for testing Lan wires RJ45.
After the acquisition, I did not immediately check it and put it on the back burner until it was in demand.
When this tester was needed - it turned out that it was not working!
A known good (factory, working) tester cable does not ring, it does not react at all to the cable from the word at all.
Very upset, as they say, a spoon is the way to dinner .