Which of the following tools must have a constant pressure switch?

A constant pressure switch is a component that maintains a uniform pressure output in certain tools, particularly those that rely on water or air for operation, such as pumps and certain types of saws. In the context of the tools listed, circular saws often are powered by electric motors that can be configured to maintain a specific pressure or force during operation, especially in industrial or high-performance settings.

This mechanism ensures that the saw operates consistently, producing uniform cuts and enhancing precision while reducing wear on both the tool and the material being cut. Unlike the other tools mentioned, which do not rely on regulated pressure for their operation, circular saws can benefit from a constant pressure switch, helping them deliver constant power and performance during use.