Asterisk command progress
Progress() – Asterisk Command – Used to message for early media
This application generates a signal that in-band progress information is provided to the calling channel. This is also known as “early audio” and “early B3”.
Early audio also needs to be supported by the carrier in order to work for the caller.
Application Progress() is typically used in conjunction with Playback and its noanswer option (previously n option).
On an unanswered SIP channel this sends the message “183 Session Progress” to the endpoint.
Applications requiring early media should use the progress() dialplan app to generate the progress message.
Let’s have an example
exten => 100,1,Progress()
exten => 100,n,Wait(1)
exten => 100,n,Playback(audiofiletoplay,noanswer)
exten => 100,n,Hangup()
ISDN incoming call – inband information and announcements BEFORE ANSWER
Use the Progress() application in your dial plan before you Answer() the line. Use the Background() application with the n flag or the Playback() application with the noanswer flag to play your announcement, so that the line is not answered automatically for you.