AudioCodes Mediant 800 User Manual page 730

CHAPTER 28 Configuring Supplementary Services
3. The switch detects the wink and then sends the MF Spill digits with ANI and (optional) Pseudo-
ANI (P ANI).
4. The FXS device collects the MF digits, and then sends a SIP INVITE message to the PSAP
with all collected MF digits in the SIP From header as one string.
5. The FXS device generates a mid-call wink signal (two subsequent polarity reversals) toward
the E911 tandem switch upon either detection of an RFC 2833 "hookflash" telephony event, or
if a SIP INFO message with a "hooflash" body is received from the PSAP (see the example
below). The duration of this "flashhook" wink signal is configured using the parameter
FlashHookPeriod (usually 500 msec). Usually the wink signal is followed by DTMF digits sent
by PSAP to perform call transfer. Another way to perform the call transfer is to use SIP
REFER messages, as described below.
6. The FXS device supports call transfer initiated by the PSAP. If it receives a SIP REFER
message with the Refer-To URI host part containing an IP address that is equal to the device's
IP address, the FXS device generates a 500-msec wink signal (double polarity reversals), and
then (after a user-defined interval configured by the parameter WaitForDialTime), plays DTMF
digits according to the transfer number received in the SIP Refer-To header URI userpart.
7. When the call is answered by the PSAP operator, the PSAP sends a SIP 200 OK to the FXS
device, and the FXS device then generates a polarity reversal signal to the E911 switch.
8. After the call is disconnected by the PSAP, the PSAP sends a SIP BYE to the FXS device,
and the FXS device reverses the polarity of the line toward the tandem switch.
The following parameters need to be configured:
■ EnableDIDWink = 1
■ EnableReversalPolarity = 1
■ PolarityReversalType = 1
■ FlashHookPeriod = 500 (for 500 msec "hookflash" mid-call Wink)
■ WinkTime = 250 (for 250 msec signalling Wink generated by the FXS device after it detects the
line seizure)
■ EnableTransfer = 1 (for call transfer)
■ LineTransferMode = 1 (for call transfer)
■ WaitforDialTime = 1000 (for call transfer)
■ SwapTEl2IPCalled&CallingNumbers = 1
■ DTMFDetectorEnable = 0
■ MFR1DetectorEnable = 1
■ DelayBeforeDIDWink = 200 (for 200 msec) - can be configured in the range from 0 (default) to
1000.
Modification of the WinkTime parameter requires a device reset.
The outgoing SIP INVITE message contains the following headers:
INVITE sip:Line@DomainName
From: <sip:*81977820#@sipgw>;tag=1c143
To: <sip:Line@DomainName>
Where:
■ Line = as configured in the Endpoint Phone Number Table
■ SipGtw = configured by the SIPGatewayName parameter
■ From header/user part = calling party number as received from the MF spill
Mediant 800 Gateway & E-SBC | User's Manual
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