I really dont know whether such a function exists. With Background(), it detects the Dtmf and immediately stops playing the voice prompt / music.
I am having a problem with dtmf detection - sometimes it works sometimes it doesnt. When i call from a SIP Phone - it works perfect. when i call in from a PRI line - using ISDN (I am using a TE407P digium card), then sometimes the digits are detected, and some other times the digits are not detected.
It however detects the * key perfectly without a problem, regardless of where they were coming in from…
I have set the dtmfrelax option to yes in my zap.conf.