Oct 22, 2009

Connect to E911 via PRI or CAMA trunk?

There are two types of circuits an enterprise can use to route 911 calls to the proper PSAPs (public safety answering points) and deliver the 10-digit caller ID: ISDN PRIs or Centralized Automatic Message Accounting (CAMA) trunks.

"ISDN is the wea port of choice from our perspective," says Guy Clinch, Avaya's government solutions director and a member of the National Emergency Number Association's PBX/multi-line telephone system technical subcommittee, because you can fit more phone lines in a PRI and assign each of those numbers to represent a separate ERL. In short, you can map your location and send more granular location information to the PSAP.

But as many as 85% of enterprises choose instead to retrofit their IP PBXs using legacy analog CAMA trunks for entry into the public safety system, Clinch says. It's cheaper, because the CAMA trunk is equivalent to on phone number, so they get charged only once.

The downside: CAMA trunks cannot deliver a custom caller ID like PRIs can, notes Mark Fletcher, chair of the multi-line telephone system...
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