This visual fault locator is a fiber-optic laser pen used to find breaks, bends, and faulty connections in optical fiber cables by shining a visible 650nm red laser down the line so problem points glow through the cable jacket. It offers a switchable 1mW output for standard fault-finding along with a higher 10mW setting for longer or harder-to-trace runs, and connects via universal FC/SC/ST adapters. It's a standard field tool for telecom installers and CATV/network maintenance technicians.