follow the link, example is there.
But You may get it even more easy by using a local channel (I just forgot about local channels while answering You the first time )
Lets assume You want to make a call where extension 100 is the internat extension (dialing some othe number in context outbound). Your callfile/originate may look like
CallerID: "Ext 100" <100>
Your context aa_call may then look like this:
exten => 100,1,SIPAddHeader(Call-Info: sip:\;answer-after=0)
exten => 100,n,Dial(SIP/100);
This should work independend from teh Asterisk-version.
The variant I supposed to use first also needs to be triggered by a local channel as there’s no other way to issue a dial-command with some options while using agi originate or callfiles