Optical Fiber Identifier can quickly identify the direction of transmitted fiber and display the relative core power without interrupting the current service. The fiber identifier recognizes modulation like, 270Hz,1KHz and 2KHz with continuous audible tone. There are four adapter heads available: Ø0.25, Ø0.9, Ø2.0 and Ø3.0. This OFI is powered by 2 pcs very normal AAA batteries.