Version 6.2  459  February 2011 
SIP User's Manual   8. IP Telephony Capabilities 
 
The following parameters are used to configure this feature: 
  EnableNRTSubscription 
  ASSubscribeIPGroupID 
  NRTRetrySubscriptionTime 
  CallForwardRingToneID 
 
8.3.8.5.2  Call Forward Reminder (Off-Hook) Special Dial Tone 
The device plays a special dial tone (Stutter Dial tone - Tone Type #15) to a specific FXS 
endpoint when the phone is off-hooked and when a third-party Application server (AS), 
e.g., a softswitch is used to forward calls intended for the endpoint, to another destination. 
This is useful in that it reminds the FXS user of this service. This feature does not involve 
device subscription (SIP SUBSCRIBE) to the AS.  
Activation/deactivation of the service is notified by the server. An unsolicited SIP NOTIFY 
request is sent from the AS to the device when the Call Forward service is activated or 
cancelled. Depending on this NOTIFY request, the device plays either the standard dial 
tone or the special dial tone for Call Forward.  
For playing the special dial tone, the received SIP NOTIFY message must contain the 
following headers: 
  From and To: contain the same information, indicating the specific endpoint 
  Event: ua-profile  
  Content-Type: "application/simservs+xml" 
  Message body is the XML body and contains the “dial-tone-pattern” set to "special-
condition-tone" (<ss:dial-tone-pattern>special-condition-tone</ss:dial-tone-pattern>), 
which is the special tone indication. 
For cancelling the special dial tone and playing the regular dial tone, the received SIP 
NOTIFY message must contain the following headers: 
  From and To: contain the same information, indicating the specific endpoint 
  Event: ua-profile  
  Content-Type: "application/simservs+xml" 
  Message body is the XML body containing the “dial-tone-pattern” set to "standard-
condition-tone" (<ss:dial-tone-pattern>standard-condition-tone</ss:dial-tone-pattern>), 
which is the regular dial tone indication. 
Therefore, the special dial tone is valid until another SIP NOTIFY is received that instructs 
otherwise (as described above). 
 
 
Note:  if the MWI service is active, the MWI dial tone overrides this special Call 
Forward dial tone