Before I get into my reply, I will point out that the OP is inquiring about this stuff specifically as it regards *extensions on a PBX which his company hosts as a vendor to/agent of the end user whose employees' phones are in question here. I think that materially affects the answers, but IANAL. Anyway... ----- Original Message -----
From: "Nathan Anderson" <nathana at fsr.com>
I'm also not sure how you propose to bind E911 details to a device instead of a telephone number. The few E911 services I've looked at all only give you the option to provision E911 information via TN. So if you propose a set-up such as what is being discussed here, where each company phone only has an internal extension # and no DID, and CLID is uniformly set to a single number for all outbound calls from any phone whether it is located in the office building or at an employee's residence, then there can only be a single E911 address for all of those phones.
And indeed, there used to be such an exemption for office PBX type installations; I do not remember whether it's expired, but I think so. There was quite a bit of third party activity in the "patching around your PBX to send remote extension building locations to the PSAP" space at the time...
The only other kludgey workaround I can think of that might pass muster would be to assign unique "throwaway" TNs to each individual extension that you would use as the CLID for outbound from that extension *only* when 911 is dialed, and continue to use the global office TN as CLID across all extensions for all other outbound calls. It's not a perfect solution, since if the individuals using those phones have no clue about those numbers, they might get confused when asked to verify their own telephone number by the PSAP and the dispatcher reads some number back to them that isn't their main office number. At that point, you might as well let the customer know that these numbers exist and give them the option of using them as DIDs for the extensions/devices they've been assigned to.
The "Emergency CNID", yes; FreePBX has this, and can be taught what are emergency calls; when it recognizes one, it sends a different CNID out on the "trunk". I believe that PSAPs have a protocol for dealing with this sort of situation, where a note can be put in the LIDB saying that this ANI is at a physical location and the phone may be labeled with a different number, but I am not a PSAP operator, so I might be wrong on this. Cheers, -- jra -- Jay R. Ashworth Baylink jra at baylink.com Designer The Things I Think RFC 2100 Ashworth & Associates http://baylink.pitas.com 2000 Land Rover DII St Petersburg FL USA #natog +1 727 647 1274