Electric trailer brakes

Electric trailer brakes are drum brakes with electromagnetic actuators powered from the tow vehicle through a brake controller. Standard in the US and Australia for trailers over 2,000 lb (900 kg). The key advantage over inertia brakes is controllable braking effort, working on uphill grades, and integration with hill-descent control.

Magnets inside the drums apply current (0–12 A) to press friction shoes against the drum face. The driver dials in effort via the gain control on a brake controller (Tekonsha P3, Prodigy P2). Each wheel has an electromagnet, an adjuster, and a breakaway switch for emergency activation. Seasonal checks: magnet coil resistance (~3.2 Ω each), shoe-to-drum clearance, drum surface condition. Rare in the UK and almost unseen in mainland Europe.