AudioCodes Mediant 800B User Manual page 430

When an IP phone subscriber dials 911, the device receives the SIP INVITE message and
makes a call to the PSAP as follows:
1. The FXO device seizes the line.
2. PSAP sends a Wink signal (250 msec) to the device.
3. Upon receipt of the Wink signal, the device dials MF digits after a user-defined time
(WaitForDialTime) containing the caller's ID (ANI) obtained from the SIP headers
From or P-Asserted-Identity.
4. When the PSAP operator answers the call, the PSAP sends a polarity reversal to the
device, and the device then sends a SIP 200 OK to the IP side.
5. After the PSAP operator disconnects the call, the PSAP reverses the polarity of the
line, causing the device to send a SIP BYE to the IP side.
6. If, during active call state, the device receives a Wink signal (typically of 500 msec)
from the PSAP, the device generates a SIP INFO message that includes a "hookflash"
body, or sends RFC 2833 hookflash Telephony event (according to the
HookFlashOption parameter).
7. Following the "hookflash" Wink signal, the PSAP sends DTMF digits. These digits are
detected by the device and forwarded to the IP, using RFC 2833 telephony events (or
inband, depending on the device's configuration). Typically, this Wink signal followed
by the DTMF digits initiates a call transfer.
For supporting the E911 service, used the following configuration parameter settings:

Enable911PSAP = 1 (also forces the EnableDIDWink and EnableReversalPolarity)

HookFlashOption = 1 (generates the SIP INFO hookflash message) or 4 for RFC 2833
telephony event

WinkTime = 700 (defines detection window of 50 to 750 msec for detection of both
winks - 250 msec wink sent by the PSAP for starting the device's dialing; 500 msec
wink during the call)

IsTwoStageDial = 0

EnableHold = 0

EnableTransfer = 0
•
Use RFC 2833 DTMF relay:
♦
♦
♦

TimeToSampleAnalogLineVoltage = 100

WaitForDialTime = 1000 (default is 1 sec)

SetDefaultLinePolarityState = 0 (you need to verify that the RJ-11 two-wire cable is
connected without crossing, Tip to Tip, Ring to Ring. Typically, the Tip line is positive
compared to the Ring line.)
Note: If the two-wire cable is crossed, the SetDefaultLinePolarityState parameter
must be set to 1.
The device expects to receive the ANI number in the From and/or P-Asserted-Identity SIP
header. If the pseudo-ANI number exists, it should be sent as the display name in these
headers.
User's Manual
RxDTMFOption = 3
TxDTMFOption = 4
RFC2833PayloadType = 101
Mediant 800B Gateway and E-SBC
430 Document #: LTRT-10286