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 (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. The feature doesn't involve device subscription (SIP SUBSCRIBE) to the Application server.

Activation/deactivation of the service is notified by the server. An unsolicited SIP NOTIFY request is sent from the Application server to the device when the Call Forward service is activated or de-activated. 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:

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From and To: contain the same information, indicating the specific endpoint

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Event: "ua-profile"

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Content-Type: "application/simservs+xml"

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Message body is the XML body and contains the “dial-tone-pattern” set to "special-condition-tone", which is the special tone indication:

<ss:dial-tone-pattern>special-condition-tone</ss:dial-tone-pattern>

To cancel the special dial tone and playing the regular dial tone, the received SIP NOTIFY message must contain the following headers:

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From and To: contain the same information, indicating the specific endpoint

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Event: ua-profile

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Content-Type: "application/simservs+xml"

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Message body is the XML body containing the “dial-tone-pattern” set to "standard-condition-tone", which is the regular dial tone indication:

<ss:dial-tone-pattern>standard-condition-tone</ss:dial-tone-pattern>

Therefore, the special dial tone is valid until another SIP NOTIFY is received that instructs otherwise (as described above).