[Asterisk-Users] Not answering PSTN until SIP answers

[Stuart Elvish]

Hi,

I was just wondering whether or not anybody has a dial plan or some 
advice on getting a SIP phone to ring without answering the PSTN line 
so that the caller doesn't have to pay for the phone call unless it 
actually get answered by a human or the answering machine after 40 
seconds. I had a look through the wiki but there wasn't anything I 
could find (probably the wrong search terms). Any advice is greatly 
appreciated.

Kind Regards
Stuart