# Reed switch The reed switch is an electrical switch operated by an applied **magnetic field**. This sensor is very important in **SimpleIndustry and SimpleMeter** devices as it takes over button functionality and is the main sensor the device is operated by (downlink requests, activation/deactivation). --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://ask.simplehw.eu/kb/sensors/magnetic-switch.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.