The #9107B Electric Brake Force Meter (3rd Gen) is an all-in-one tool for testing vehicle tow circuits and brake systems without a trailer. It simulates dynamic trailer loads to verify proper function of brake controllers and towing lights. The 25-ft cable allows for easy, one-person, in-cab testing. This device checks truck-side brake controller output, tail lights, turn signals, 12V+, reverse, and ground conditions, ensuring all towing-light functions work correctly. Comes with a soft nylon case for easy storage and transport.