Implementing E911 On-prem: Automatic Location Identification

source：www.nojitter.com

In a previous No Jitter article, Implementing E911 On-prem: Goals, Issues, Approaches, my colleague Dennis Bell provides an excellent introduction and overview regarding the preparations and considerations for complying with this recent legislation. My article focuses specifically on providing the critical dispatchable location information required by RAY BAUM’s Act and other similar legislation.

With a 911 call, a dispatchable location connects to the public safety answering point (PSAP)—and consists of the calling party's validated street address, suite number, apartment, or similar information necessary to identify the calling party's location adequately.Finally, I’ll review how location information can be customized and improved through the combined use of PS-ALI service and on-premises E911 applications available in today’s UC systems.

Let’s take a moment to discuss what dispatchable location information gets passed on a 911 call under typical conditions. Next, I’ll discuss the role of private switch/automatic location identification (PS-ALI) service and its early use to improve dispatchable location information when service address information, as delivered by the telephone system, was insufficient.

The Automatic Location Identification (ALI) record sent to the emergency communications center/PSAP consists of the service address for the customer location where the service was delivered and based on the automatic number identification (ANI) that matches the Caller ID.

For single-site locations of reasonable size and only one floor, this service address information is often sufficient to provide a dispatchable location. However, for larger sites, i.e., buildings with multiple floors, multi-building campus environments, and networking sites that share centralized PSTN services—the standard service address in the ALI record typically doesn’t contain enough descriptive information to adequately direct first responders to the source of a 911 call.

On digital services (ISDN or PRI), the Caller ID can be configured and assigned to the outbound call by the enterprise’s phone system. So, theoretically, a distinct ANI record could be assigned to each station on the phone system. However, without adding PS-ALI service, all ANIs sent out would have the same carrier assigned service address in the ALI record. PS-ALI service assigns a unique 911 location database entry to each station/DID. When the PS-ALI database merges with the 911 database, the custom address information can be passed to the emergency communications center or PSAP, providing the required dispatchable location information for first responders.

Monthly costs for PS-ALI services are in proportion to the number of DID/PS-ALI records. A large enterprise could easily incur hundreds or thousands of dollars per month for PS-ALI service if it created a unique 911 database entry for each station/DID number.

Premise UC System E911 Applications
Current UC systems have provided the software capability to assign customized address information and build 911 “zones” or “user groups” rather than be forced to assign a PS-ALI record to every DID user. This capability can supersede the standard service address information associated with the trunks normally passed as the ALI on an outgoing 911 call. But building this database in the premise telephone system still requires the use of PS-ALI service.

That’s because the UC system cannot directly transmit this customized information to the 911 network. The 911 network is a separate and closed network—it doesn’t allow unauthorized entities to put their ALI information into the address databases that are part of the 911 network. Therefore, an intermediary is necessary to provide the authorized “bridge” between the customized 911 information configured in the premise UC system and the actual 911 ALI databases.

PS-ALI and Custom E911 Zones
E911 zones allow administrators to group users as needed (by building, floor, or even smaller, more granular areas), resulting in far fewer PS-ALI records required than in a one-to-one design; this can significantly reduce the cost of PS-ALI service.

PS-ALI Zone records are assigned a unique 10-digit emergency location identification number (ELIN) representing the emergency response location (ERL) zone that it serves. PS-ALI worksheets are main