This SAE Recommended Practice covers the wiring and rectangularly shaped connector standards for all types of trailers whose gross weight does not exceed 4540 kg (10 000 lb). These trailers are grouped in SAE J 684, with running light circuit loads not to exceed 7.5 A per circuit. This document provides circuits for lighting, electric brakes, trailer battery charging, and an auxiliary circuit color code and protection for the wiring from hazards or short circuits. Color code is compatible with SAE J 560 and ISO 1724-1980(E).