The GN Nettest VFL-650 Visual Fault Locator is a handheld, visible laser source that emits a bright beam of laser light into a fiber, allowing the user to visually detect a fiber fault for up to 5 km. Now you can easily isolate high losses and faults in optical fiber with the VFL-650 Visual Fault Locator. This handheld, visible laser source emits a bright beam of 650 nm light into a fiber, allowing the user to see a fiber fault as a glowing or blinking red light. A red LED indicates when laser power is active. Power is supplied by a single AA battery in the VFL-650, which allows up to 24 hours of continuous operation.