A visual fault locator is a compact, handheld device that emits a visible light beam, typically in the red wavelength range, through a fiber optic cable. A VFL is used to detect faults, breaks, or bends in fiber optic cables by emitting a bright red light that is visible even through the fiber's jacket. It's a cost-effective and. There are different types of a computer and different sorts of light indicators on a computer tower for various models. 4 LED lights often flash red if there is a problem with your motherboard. Or it could be caused by the quality of the connector itself, such as poor end-face geometry that doesn't pass the. Hopefully, we can resolve this quickly. for installing electrical products and systems. Existence of a standard shall not preclude any member or nonmember of NECA or FOA from specifying or using.