The Fibrain FB9214 visual fault locator (tester of fiber’s continuity) is an indispensable device for detecting discontinuities of a fiber-optic link and points of optical power leakage, such as macrobends, breaks of fiber and splices, open connections, etc. The Fibrain FB9214 locator is compatible with both single-mode and multi-mode fibers. A tester emits red light of 650 nm wavelength and can operate in a continuous mode or with two different modulation frequencies. The optical power emitted is constant regardless of the battery charge level because of a stabilized power supply used in the device. Original Japanese diodes applied guarantee a long lifetime, no darkening with time, and low power consumption, and hence a long battery life as well as high efficiency of power coupling into a fiber, which assures long ranges despite using optically safe laser power. A rotary ring that secures the switch prevents the device from accidentally turning on in a bag and battery discharge. The FB9214 locator is normally delivered in a protective case.