We have installed station alerting devices in our fire stations. This allows our firefighters to be alerted to an incident through the system. It utilizes overhead speakers and lights to do this. The system is a Honeywell USDD G2 Station Alerting system
https://buildings.honeywell.com/us/en/brands/our-brands/usdd. The specific device in each of the stations is a ATX Station Controller. The system allows SIP connection to allow connection to a phone system so overhead paging can occur over the system. This allows not only internal paging for that station but our dispatch center can connect and give additional information after the initial dispatch.
We have been working to try and get our Mitel system to connect without success. Our outside phone vendor has some basic SIP knowledge but it appears this is beyond his scope of expertise. The vendor of the ATX has told us that the system is built on PJSIP but can provide no other information other than what is in the manual which is:
The ATX has a built-in SIP client for receiving VoIP phone calls. The ATX can be configured to register one or more extensions with a phone
switch that supports SIP, and when a call is directed to one of the extensions the ATX will answer the call and route the audio to the station