> 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/trunking/en/was-ist-die-fallback-rufnummer-bei-sipgate-trunking.md). # What is the fallback number in sipgate trunking? If you configure a caller ID in your phone system, it will automatically be transmitted to the called party. If this is not the case, or the caller ID cannot be transmitted in the format we require, sipgate sets a so-called fallback number. This can be set on the website in the **trunk settings** can be set. ![Fallback number dialog](/files/c90b78f2c22959e7ba49bf3c8a720ef863907bb8) For outgoing calls, please set the desired caller ID in the **E164**-**format** (i.e. internationally without leading zeros or **"+" sign**) as a new header: ``` P-Preferred-Identity: ``` If you want to **hide your caller ID** please adjust the header as desired: ``` P-Preferred-Identity: Privacy: id ``` --- # 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: ``` GET https://help.sipgate.de/trunking/en/was-ist-die-fallback-rufnummer-bei-sipgate-trunking.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.