Which statement best describes a reed switch?

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Reed switches are magnetic-sensitive devices that use two ferromagnetic reeds sealed inside a glass envelope. In the absence of a magnetic field, the reeds stay apart and the circuit is open. When a magnetic field is nearby, the reeds attract and close the contact, completing the circuit. This direct, field-driven action makes the description match a magnetic-sensitive switch with two ferromagnetic reeds that contact when in a magnetic field. They’re different from capacitive proximity sensors, light-activated switches, or temperature-controlled switches, which respond to capacitance changes, light, or temperature, respectively.