There are TDM interfaces higher end PBX's use to interconnect to the PS/ALI. I beleive it's a CAMA trunk that signals using MF.
----- Original Message ----- From: "John Todd" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Thursday, August 21, 2003 3:00 PM Subject: [Asterisk-Users] RE:911, networks of * servers, etc. (was: VOIP Dialtone?) > > Yes, I'm familiar with the E911 platforms and their requirements to > some degree. The trick is that the people running Asterisk PBX > systems have no visibility into SS7, and that is an unreasonable > expectation, so some other out-of-band method for moving caller > location to the PSAP is required. > > As far as geographic location tracking is concerned: that is the > user's problem. If they don't have the correct information in their > device, then they're SOL. There is _no way_ to develop lat/lon/alt > coordinates from an IP address, despite what any .com > flash-in-the-pan company says they can do with their clever > databases. Thus, the PBX/switch provider will have to enforce their > own database of device-to-geographic-coordinates. (As mentioned, > maybe a SIP header is a reasonable thing to use for the UA to relay > this data to the proxy.) I am not concerned so much about the > ability of the devices to send their data to the proxy: I am VERY > concerned about how the proxy then looks up the appropriate PSAP, and > then relays the data for the call to that PSAP. > > JT > > > > > >911 through the phone system is tricky business. e911 which is the > >automated process of handing the address to the 911 center uses the SS7 > >database to do it's work (the database is created when the LEC runs > >physical lines to locations not by people filling anything out). Cell phone > >service providers have the simuliar problems as VoIP service providers are > >facing are realizing with call forwarding and call following it will get > >worse.. Congress has mandated that the cell phone industry make it possible > >to track a cell phone users within 300yards via cell sites and > >triangulation. By 2005 every cell phone will be required to have a GPS and > >send GPS information to the 911 system when they call 911. If you want more > >information on e911 try http://www.fcc.gov/911/enhanced/ . As the cell > >phone industry grows there will be a need for a national 911 call routing > >center. I bet it won't be free. > > > > > >Original Message: > >----------------- > >From: John Todd [EMAIL PROTECTED] > >Date: Thu, 21 Aug 2003 01:32:24 -0700 > >To: [EMAIL PROTECTED] > >Subject: [Asterisk-Users] 911, networks of * servers, etc. (was: VOIP > >Dialtone?) > > > > > > > >OK, that "VOIP dialtone?" thread was getting really out of hand, so > >I'll condense my answers into one big ugly message: > > > > > >1) 911 service. Yes, that is one of three reasons to keep your PSTN > >line. The other two reasons are: Inbound calls from local callers > >still should work on a POTS line, for now. You can't find VOIP > >providers in most area codes, so you'll most likely need to have a > >"local" number that finds it's way to you for "local" tasks. > >Secondly, the Internet is not as reliable as the phone system. > >Sorry, folks, it just works that way right now despite what your > >network engineer might tell you. That's not to say it's unreliable, > >but those last two nines are very expensive... Besides, any good > >network engineer will tell you that you should have multiple paths > >for your IP connectivity. With few exceptions, most homes do not > >have multipath connectivity. (note: businesses may in fact have > >better uptime on their IP network than their phone network, if they > >have competent engineers and a reasonable budget.) > > > >1.5) There are reasonable technical solutions to this problem, but > >for the life of me I can't figure out why the 911 centers haven't > >gotten their act together and solved this. There are two halves to > >this problem: "What PSAP do I call? (and what phone number)" and > >"How do I get my location data to the PSAP once I call them?" > >C'mon, this is not difficult. The first question can be answered > >trivially: there _must_ be a database of address-to-PSAP mappings. > >Any PBX administrator (or SIP phone owner, for that matter) should be > >able to figure out their address. Methods for associating the PSAP > >number with the phone are numerous, and trivially implemented - if > >people don't keep their address information updated, they're SOL > >(though you can remind them in an automated fashion to keep it > >updated - just forbid them from using the service unless they verify > >the address every month or so.) > > > >The second question is more difficult, but certainly possible. There > >may be kludge ways of doing it, and there should be more elegant ways > >of doing it. A SIP header with lat/lon/alt data that gets sent from > >the UA only on 911 (or other programmable string) calls might be > >reasonably elegant... maybe. But that only gets the data to the SIP > >proxy. That doesn't solve the issue of how you get that data from > >the SIP proxy to the PSAP, which at some point will be almost > >certainly through a PSTN connection... ADSI FSK, maybe? Ugly, and > >PSAPs would not want to invest in equipment. A national caller-id to > >location clearinghouse in which your proxy could participate (any 911 > >calls would create a temporary mapping)? Maybe, but probably not. > >Non-standard, and I doubt PSAP operators would want another tool, > >even if it is web-based and so easy a monkey could use it. I don't > >know. I guess I'll grill the PSAP people at the panel next month at > >VON. :-) > > > [snip] > _______________________________________________ > Asterisk-Users mailing list > [EMAIL PROTECTED] > http://lists.digium.com/mailman/listinfo/asterisk-users > _______________________________________________ Asterisk-Users mailing list [EMAIL PROTECTED] http://lists.digium.com/mailman/listinfo/asterisk-users
