> For the complete documentation index, see [llms.txt](https://prosbcdocs.telcobridges.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://prosbcdocs.telcobridges.com/telecom-references/sip-and-voip/nse.md). # NSE NSE (Named Signaling Events) is a proprietary protocol to switch from voice to passthrough for fax/modem communication without involving SIP. It uses a proprietary event, based on NTE (Named Telephone Events). NTE is not proprietary, but NSE is. ### TelcoBridges and NSE We currently support NSE events: ``` 192 (switch to passthru) 193 (disable echo) 194 (switch back to voice) ``` This adds a new SIP SDP entry that looks like this for initial negotiation: ``` a=rtpmap:100 X-NSE/8000 a=fmtp:100 192-194 ``` The system does not send a SIP re-invite, but instead will send this NSE event 192. #### Call Flow ![NSE call flow](https://docs.telcobridges.com/w/images/1/12/NSE_call_flow.png) ### Configuration * [Toolpack v2.7: NSE configuration](https://github.com/telcobridges-main/tmedia-wiki/tree/main/reference/voice-media/modifying-fax-relay-profile-settings/README.md) ### References * [RFC 2833](http://tools.ietf.org/html/rfc2833) * [list of NSE events](https://supportforums.cisco.com/docs/DOC-1381) --- # 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://prosbcdocs.telcobridges.com/telecom-references/sip-and-voip/nse.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.