ATX, which stands for Advanced Technology eXtended, is a standard specification for computer power supplies and motherboards. It provides a set of guidelines and requirements for the physical dimensions, connectors, power capacities, and other features of these components. It was designed to make sure that all the components inside a computer can work together smoothly, even if they're made by different. ATX (Advanced Technology Extended) is responsible for this standard. Some power supplies have a manual switch for selecting input voltage, while others automatically.