User's Manual 308 Document #: LTRT-10532
Mediant 500L Gateway & E-SBC
ensures that the call is routed to an appropriate PSAP, based on ELIN-address match
lookup in the emergency service provider's ALI database.
The figure below illustrates an AudioCodes ELIN device deployed in the Skype for
Business environment for handling E9-1-1 calls between the Enterprise and the emergency
service provider.
15.8.3.1 Detecting and Handling E9-1-1 Calls
The ELIN device identifies E9-1-1 calls and translates their incoming E9-1-1 calling
numbers into ELIN numbers, sent toward the PSAP. The device handles the received E9-
1-1 calls as follows:
1. The device identifies E9-1-1 calls if the incoming SIP INVITE message contains a
PIDF-LO XML message body. This is indicated in the SIP Content-Type header, as
shown below:
Content-Type: application/pidf+xml
2. The device extracts the ELIN number(s) from the "NAM" field in the XML message.
The "NAM" field corresponds to the <CompanyName> column in the Location
Information Server (LIS). The device supports up to five ELIN numbers per XML
message. The ELINs are separated by a semicolon. The digits of the ELIN number
can be separated by hyphens (xxx-xxx-xxx) or they can be adjacent (xxxxxxxxx), as
shown below:
<ca:NAM>1111-222-333; 1234567890 </ca:NAM>
3. The device saves the From header value of the SIP INVITE message in its ELIN
database table (Call From column). The ELIN table is used for PSAP callback, as
discussed later in ''PSAP Callback to Skype for Business Clients for Dropped E9-1-1
Calls'' on page 310. The ELIN table also stores the following information:
• ELIN: ELIN number
• Time: Time at which the original E9-1-1 call was terminated with the PSAP
• Count: Number of E9-1-1 calls currently using the ELIN
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