What is a reed switch primarily used for?

A reed switch is primarily used to control the flow of electricity in a circuit. It functions as an electromechanical switch that operates by the presence of a magnetic field. When a magnet approaches the reed switch, it causes the internal contacts to either close or open, allowing or interrupting the flow of electrical current. This makes the reed switch particularly useful in applications where magnetic actuation is desired, such as in security systems, alarm systems, and various automation tasks.

The other uses listed, such as controlling mechanical motion, converting electrical signals, and detecting temperature changes, do not accurately represent the primary function of a reed switch. While reed switches may indirectly influence mechanical systems when used to control circuits, their primary design and function focus on circuit control rather than direct mechanical movement, signal conversion, or temperature sensing.