When a subscriber dials an emergency number (typically 911or 112) from within the corporate network, Lotus Sametime Unified Telephony uses the subscriber's current IP address to lookup the associated Emergency Calling data for this subscriber. It retreives an ELIN (Location Information Number) and the Route number for egress to the gateway of the calling user's PSAP (Public Safety Answering Point) jurisdiction.
In order to provide the Emergency Calling feature, Lotus Sametime Unified Telephony requires a Lotus Sametime Unified Telephony or Cisco PSTN gateway to provide the break-out to the adequate local central office (ultimately a PSAP jurisdiction) corresponding to a subscriber's current location within the corporate network.
Other adjunct equipment like the Telident S.T.S.
(Station Translation System) or the Tone Commander Call Locator
can provide additional gateway functionality and emergeny call management/auditing.
Functional Sequence for Mobile Users (no SBC)
As a prerequisite, the subscriber's device has obtained a "location-dependent" dynamic IP address. See the topics on Location Identification
for details on how this can be achieved.
Figure 1. Emergency Call Flow
- A caller places an emergency call by sending an INVITE to Lotus Sametime Unified Telephony.
- Lotus Sametime Unified Telephony, via translation, detects an Emergency call and uses the caller's IP address to look up and retrieve an appropriate LIN and Route number from the Emergency Calling Subnets (E911) table. The LIN is inserted in the INVITE.
If the caller's IP address is not found, the call cannot be routed correctly and it is either routed to an on-site answering position or an announcement is played.
- The Route parameter (via translation) leads the call to a particular gateway that is served by the public network's E911 tandem office. It can then route the call to the proper PSAP jurisdiction serving the caller.
If an emergency call cannot be routed to a PSAP operator, the call can be optionally routed to an E911 Default Emergency Number (Directory Number format) as an added precaution.
If a Lotus Sametime Unified Telephony is serving multiple geographic locations, and E911 service is a requirement, links (and routes) to each responsible PSAP will be required.
Parent topic: Emergency Calling