What i s areed switch and how does it work?

A reed switch is an electromagnetic switch that operates using a pair of ferromagnetic contacts sealed within a glass envelope. When a magnetic field is applied, the contacts close, allowing current to flow; when the magnetic field is removed, the contacts open, breaking the circuit. Reed switches are commonly used in applications like door sensors and security systems due to their reliability and simplicity. They can be activated by a magnet from a distance, making them ideal for contactless operation.