Main Page | See live article | Alphabetical index A reed switch is an electric switch that consists of a pair of metal contacts in a sealed glass envelope. A permanent magnet placed in close proximity to the switch will cause the contacts to pull together, thus completing an electrical circuit. Reed switches are commonly used in mechanical systems as proximity switches as well as in door and window sensors in burglar alarm systems. This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License.