> For the complete documentation index, see [llms.txt](https://help.sipgate.de/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://help.sipgate.de/cloud-telefonanlage/en/using-sipgate/telefonie/was-bedeutet-dtmf.md). # What does DTMF mean? DTMF means **Dual-Tone Multi-Frequency** (dual-tone multi-frequency). Put more simply, these are key tones. **When do I need DTMF?** For calls to a **voice computer**, which requires input via key tone, this is done via DTMF. DTMF is also used for a call to the **sipgate voicemail** , since it asks for a PIN via key tone. But DTMF is also needed for various telephony features such as **call swapping and transferring** . --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## 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, and the optional `goal` query parameter: ``` GET https://help.sipgate.de/cloud-telefonanlage/en/using-sipgate/telefonie/was-bedeutet-dtmf.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. 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.