Playback() — Plays the specified audio file to the caller
Plays back a given filename to the caller. The filename
      should not contain the file extension, as Asterisk will automatically
      choose the audio file with the lowest conversion cost. Zero or more
      options may also be included. The skip option causes the playback of the message
      to be skipped if the channel is not in the “up” state (i.e., it hasn’t
      yet been answered). If skip is
      specified, the application will return immediately should the channel
      not be off-hook. Otherwise, unless noanswer is specified, the channel will be
      answered before the sound file is played. (Not all the channels support
      playing messages while still on-hook.) If j is passed as one of
      options and the file does not exist, this
      application jumps to priority n+101
      (where n is the current priority), if
      it exists.
exten => 123,1,Answer()
exten => 123,n,Playback(tt-weasels)