SIP User's Manual  422  Document #: LTRT-12804 
  Mediant 800 MSBG 
 
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. 
 
 
Note:  Modification of the WinkTime and FlashHookPeriod parameters require 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 using the SIPGatewayName parameter. 
  From header/user part = calling party number as received from the MF spill. 
The ANI and the pseudo-ANI numbers are sent to the PSAP either in the From and/or P-
AssertedID SIP header.