bkelly1676
Technical User
Could anybody give me a simple definition of CAMA Trunks and what the do and how they areused for E911.
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CAMA Trunks?
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inbound cama trunks are used on positron consoles in this part of the world, i have used them in an 81c for that purpose.. they work like any other trunk, with a few exceptions.. they are wired for called party hold.. hangup on a 911 dispatcher and pick the phone up 10 minutes later, unless she did a rls, she will still be on the trunk.. the central office sends ani and ali info inbound on those trunks.. that can tie into any database using calling party info as a get file command...
in other words she gets your number, and address.. and she can get your call history and any other the info the city, county state or fed data base has.. pretty old way of doing business but they work
john poole
bellsouth business
columbia,sc
in other words she gets your number, and address.. and she can get your call history and any other the info the city, county state or fed data base has.. pretty old way of doing business but they work
john poole
bellsouth business
columbia,sc
I'm sure someone can post a technical definition, but my recollection from a former install (15 years ago) is that they're basically like a 4-wire E&M, and the PBX transmits 7-digits towards the CO. I seem to remember a limitation that you couldn't used the same set of cama trunks for multiple area codes.
In our environment (rolm 8000's)the PBX sent 4 digit extension to a Telident box on a TIE trunk, and the Telident box had a tie-to-CAMA transaltor. It prepended our exchange, and then sent the call on to the CO. We had a companion software product that we used to put a physical location to a DID. That software transmitted to a data center somewhere, which them merged the data into the PSAP's database.
That installation has subsequently been replaced with PRI trunks and gained improved functionality. They still have the software to do the DID-to-location update, but any trunk can be used for a 911 call, and every call provides location information, instead of being limited to the physical quantity of CAMA trunks. At that time they ran around $175/trunk, and we were required by state law to have at least two, so two trunks paid for a full PRI.
Does that answer the question? I know there were a couple of LEC's out there that don't have the correct e911 software in their CO's, so they can't use PRI for those calls. A shame really. I hope by now that has been corrected.
In our environment (rolm 8000's)the PBX sent 4 digit extension to a Telident box on a TIE trunk, and the Telident box had a tie-to-CAMA transaltor. It prepended our exchange, and then sent the call on to the CO. We had a companion software product that we used to put a physical location to a DID. That software transmitted to a data center somewhere, which them merged the data into the PSAP's database.
That installation has subsequently been replaced with PRI trunks and gained improved functionality. They still have the software to do the DID-to-location update, but any trunk can be used for a 911 call, and every call provides location information, instead of being limited to the physical quantity of CAMA trunks. At that time they ran around $175/trunk, and we were required by state law to have at least two, so two trunks paid for a full PRI.
Does that answer the question? I know there were a couple of LEC's out there that don't have the correct e911 software in their CO's, so they can't use PRI for those calls. A shame really. I hope by now that has been corrected.
no there are still areas that require cama trunks. and yes a pri can be used just as well.. rolm 8000 was a good box and the 7000 had data switching in the late 70's.. we degress... not all cama;s are 4 wire, most are.. a 4 wire trunk takes 3 pair per trunk, not a pretty site
john poole
bellsouth business
columbia,sc
john poole
bellsouth business
columbia,sc
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bkelly1676
Technical User
Thank you very much Guys, this is exactly what i was looking for. I have in tha past always had PRIs and now the company i work for uses several T-1s and want a solution. It sounds like my best bet is to just go with PRIs for all my sites. Your help is greatly appreciated!!!! Any other information or sugestions would also be appreciated.
ah yes, dataswitching... forgot about that!
good point about the 4wire thing. They tried to install us as a 2wire with no end of trouble, so they switched. (We were the first in the state or county [can't remember which] to do PS/ALI). I'd forgotten about the called party hold, tho....
I'd heard some reservation about using PRI for 911 due to customer provided CPN, but as long as the CO screening tables are set correctly, there shouldn't be a problem.
good point about the 4wire thing. They tried to install us as a 2wire with no end of trouble, so they switched. (We were the first in the state or county [can't remember which] to do PS/ALI). I'd forgotten about the called party hold, tho....
I'd heard some reservation about using PRI for 911 due to customer provided CPN, but as long as the CO screening tables are set correctly, there shouldn't be a problem.
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