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* Pre-Call announcement with B2BUA Application Module *
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Description:
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The annoucement server plays a wav file to the caller.
It searches for files to play following these rules:
1) [AnnouncePath]/[Domain]/[User].wav
2) [AnnouncePath]/[User].wav
Then it connects the caller to the r_uri in Back-To-Back
User Agent (B2BUA) mode, thus staying in the signalling path
of the call.