is it expecting some kind of signal that you can send to reduce the wait ? 16 seconds from off-hook to dialtone doesn’t sound right … surely the users of the PBX would have throttled you by now ?
the problem with pots channels is that unless you have ‘answer supervision’ (almost none do) then it is impossible to tell when ringing stops and call is answered. Thus your only real option is to wait for the pbx to pick up after a known interval…
using a PRI or VoIP (sip/iax2) line this problem does not occur, it correctly informs asterisk when the remote party answers.
If you use Waitforsilence(4250,1) you will basically get answer supervision on a pots line if you are calling the US as the silence between rings is 4 secs. In other coutnries, the delay is shorter which I wish was the case for me.