A 15A inlet box is a small, weatherproof fitting mounted on the outside wall of a caravan, usually made from UV-resistant plastic. It's typically about the size of an adult hand. From the outside, you'll see: A hinged flap or cover that keeps out rain, dust, and insects when it's not in use. A 15-amp socket recessed inside the box. This socket has three holes arranged in the Australian standard pattern (active, neutral, and earth). Some models have a locking latch or a way to secure the plug so it can't be pulled out accidentally. When you lift the flap, you plug the male end of a 15A caravan power lead into the inlet box. The plug fits snugly and is protected by the cover while connected. Inside the caravan wall, the back of the inlet box has: Three electrical terminals where the active (brown or red), neutral (blue or black), and earth (green/yellow) wires are connected. A cable clamp that grips the electrical cable so tension on the lead isn't transferred to the terminals. A sealed housing that helps keep moisture out. Unlike a household power point, the inlet box doesn't supply power to other devices. Its only job is to receive 240V power from an external source and pass it into the caravan's electrical system, where it then goes to the safety switch (RCD), circuit breakers, and the caravan's appliances. In simple terms, it's like the caravan's fuel filler cap, except instead of taking in fuel, it takes in electricity from an external power supply.