A magnetic reed switch is a fast-acting switch with a single pole, single throw that uses which type of contact?

• A. NC contact
• B. SPDT
• C. SPST
• D. NO contact

Answer: (D)

A reed switch is a magnetically actuated, fast-responding switch with two reeds sealed in a glass envelope. In normal conditions the reeds are apart, so the circuit is open. When a magnet is brought near, the magnetic field pulls the reeds together and they touch, creating a conducting path. This means the contact type is normally open: it remains open until a magnetic field is present to close it. The single pole, single throw description fits because there is one path that can be either open or closed, with no extra outputs. A normally closed variant would be closed by default and open when a magnet is near, which is less typical for standard reed-switch use. A single pole double throw configuration would offer a second selectable path, which a basic reed switch does not provide.