I have been using Sangoma A102 card with wanpipe-3.5.28 and FS 1.2.8.

At a couple of different customer sites, common issue reported is, when a call is made from external world (mobile/fixed line), although the destination extension rings, no ringback is heard at the caller end.

Extension dialplan is to bridge to the desired extension, something like:

 <action application="bridge" data="user/3001" />

On capturing the isdn traces, I see that packet exchanges involve SETUP, CALL PROCEEDING, and ALERTING (with a progress indicator saying "Call is not end-to-end ISDN - progress information available in-band")

After experimenting a bit, what I find is, ringback is heard if I were to modify my dialplan as follows:

<action application="ring_ready" />
<action application="set" data="ringback=$${uk-ring}"/>
<action application="bridge" data="user/3001" />

This time, ISDN traces have the following: SETUP, CALL PROCEEDING, ALERTING (with a progress indicator saying "Call is not end-to-end ISDN - progress information available in-band"), and PROGRESS (with a progress indicator saying "In-band information or an appropriate pattern is now available")

My question is, while working with FreeTDM, do I need to always set ringback explicitly? Could somebody please help me understand this correctly?

Thanks!