This product injects over current wire and the diode should light up on both sides in succession (there are two speeds). If an LED does not light, it is that there is a worry. It works with a 9V battery (6LR61). If you want to test a crossover cable, it's less intuitive because the remote party, the LEDs light up in the following order: 3-6-1-4-5-2-7-8 . My advice: pair your cable with another crossover cable.
