exten = s,1,Answer()
exten = s,n,Wait(1)
exten = s,n,Playback(welcome_3seconds)
exten = s,n,Dial(...)
Dail(…) takes some time so I would like to start dialing while welcome sound is played. Both Playback() and Background() apps wait until sound finishes and then returns control do Dial().
Is it possible?