<aside> ⚠️ WARNING: The UC system has PSTN connectivity, but no 911 connectivity. Calls to 911 will not go through, even if site to site connectivity is established.

</aside>

The system currently has a limited connection to the PSTN - the public switched telephone network - this means calls to 911 will not work.

There are plans to enable PSTN connectivity - but even with this connectivity calls to 911 will be hard to support.

Why 911 will be hard to support even once PSTN connectivity is established:

Key terms:

• PSAP - Public Safety Answering Point

The PSAP is the physical building that 911 calls are answered in. The FCC has a list of all of the PSAPs near you.

• ANI - Automatic Number Identification

This is a process to identify the number you are calling from.

• ALI - Automatic Location Identification

This is a process to identify where you are. It is generally not that great at identifying location for anything that isn’t an old-school landline.

• DID - Direct Inward Dialing

A DID is a phone number - it can be assigned to a endpoint (a phone) or a resource such as a IVR, queue, or something else.

• CAD - Computer-Aided Dispatch

Software that the call taker/dispatcher use to accept your call, log relevant information, and ultimately dispatch emergency services.

• i3 - NexGen PSAP

A technology standard for modern PSAP facilities that relies on JSON and HTTP APIs for 911.

Problems we will face supporting 9-1-1:

• How will phones present their DID when calling 911? Will this require every phone to have a globally unique DID so the 911 PSAP can call back?