1IDENTIFICATION OF DIRECTION: Correctly determine the optical fiber's direction. The left and right direction lights indicate the signal direction when an optical fiber signal is present. When the left direction light turns on, it is clear that the light is coming from the right side of the room. 2EFFICIENT IDENTIFICATION: With sound alerts, the fiber identifier efficiently distinguishes between traffic direction and frequency tones (270Hz, 1KHz, and 2KHz), and inform you. 310KM MEASUREMENT DISTANCE: Built in VFL red light source can measure a distance of approximately 10KM, which is able to meet most of your Identification requirements. 4ABS MATERIAL: Optical fiber detector is made of premium ABS material, which is wear and scratch resistant and has a long service life. 5EASY CARRYING: With the optical fiber's compact design and light weight, this optical fiber identifier is portable and simple to use.