Emergency E911 Phone Number Services; Fxs Device Emulating Psap Using Did Loop-Start Lines - AudioCodes Mediant 800B User Manual

User's Manual

26.11 Emergency E911 Phone Number Services

This section describes the device's support for emergency phone number services. The
device supports the North American emergency telephone number system known as
Enhanced 911 (E911), according to the TR-TSY-000350 and Bellcore's GR-350-Jun2003
standards. The E911 emergency system automatically associates a physical address with
the calling party's telephone number, and routes the call to the most appropriate (closest)
Public Safety Answering Point (PSAP), allowing the PSAP to quickly dispatch emergency
response (e.g., police) to the caller's location.
Typically, the dialed emergency number is routed to the appropriate PSAP by the
telephone company's switch, known as a 911 Selective Router (or E911 tandem switch). If
the PSAP receives calls from the telephone company on old-style digital trunks, they are
specially formatted Multi-Frequency (MF) trunks that pass only the calling party's number
(known as Automatic Number Identification - ANI). Once the PSAP receives the call, it
searches for the physical address that is associated with the calling party's telephone
number (in the Automatic Location Identification database - ALI).

26.11.1 FXS Device Emulating PSAP using DID Loop-Start Lines

The device's FXS interface can be configured to emulate PSAP (using DID loop start lines),
according to the Telcordia GR-350-CORE specification.
Figure 26-3: FXS Device Emulating PSAP using DID Loop-Start Lines
The call flow of an E911 call to the PSAP is as follows:
1. The E911 tandem switch seizes the line.
2. The FXS device detects the line seize, and then generates a wink signal (nominal 250
msec). The wink can be delayed by configuring the parameter DelayBeforeDIDWink to
200 (for 200 msec or a higher value).
3. The switch detects the wink and then sends the MF Spill digits with ANI and (optional)
Pseudo-ANI (P ANI).
Version 7.0
26. Configuring Supplementary Services
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