The coupled power, along with the use of the 650nm highly visible wavelength, makes the Optical Fiber Checker a low cost and effective pen style visual fault locator. It's an excellent tool for locating a broken fiber or splice, isolating a damaged connector on a patchcord. The unit operates in both an always on, CW mode, or a 3hz modulation mode for enhanced fault location capability in well lit areas. The Optical Fiber Checker is powered by two AAA batteries and comes with a compact carry case. Note: The cable is not included