911 without CAMA

[flash2200]

Hi all,

Apologies for the dumb question but...I understand that 911 system in North America used CAMA signaling protocol. From what I can tell this protocol is used exclusively with analog connection types. I'm wondering how 911 works with digital connection types such as ISDN PRI/BRI etc? If a company does not have any analog CAMA connections out to the PSTN how does the 911 get treated?

[Chris Deren]

enhanced 911 works on PRI trunks or CAMA analog trunks. You'd use CAMA in absence of PRI if e911 is required. If you don't need e911, then FXO trunks will suffice for 911 dialing.

Chris

[flash2200]

Thanks for the quick response! Cheers

[lbouchar]

There is no technical reason why 911 would not work on PRI trunks.

However, some service provider *may* overwrite the calling party number offered at call setup if the called number is 911: this varies from lec to lec. When ANI is overwritten, the LEC will typically use the Bill To Number, or main directory number on the trunk group.

This is mostly a policy decision by the LECs, not something imposed by technology.

[lbouchar]

The emergency calls section of the Unified Comunications SRND offers some guidance. There is a section specifically addressing your question.

http://www.cisco.com/en/US/products/sw/voicesw/ps556/products_implementation_design_guide_chapter09186a008085f61e.html#wp1043607

Hope this helps!

Luc

[flash2200]

I'll have a look at this. Thanks!