If you find a way that works I hope you'll post it. In the meantime, since no one else has answered, I will suggest a way that might give you what you want.
First, try setting it so that incoming calls do NOT ring Phone 2. Now place an incoming call to your GV number. When it rings, pick up Phone 2 and you should hear dial tone. Press # only and after a second or so it should answer the call.
Now go into OBi Expert Configuration / Enter OBi Expert and go to SP1 Service. You are interested in two settings under Calling Features. The first is CallForwardOnBusyEnable which should be checked. The second is CallForwardOnBusyNumber and that is the one I am not entirely certain of. Try
ph2 and if that doesn't work, try
ph2(#) as suggested by mife in the thread at
http://www.obitalk.com/forum/index.php?topic=5525.0Note that you need to make sure that the two checkboxes at the right hand side of the page (under Device Default and OBiTALK Settings) are unchecked next to those two lines before you can change the values. You may have to first submit the page with the boxes unchecked before it will let you enter new values.
If it works, you should get the behavior you want, and if it doesn't, I'd try e-mailing
support@obihai.com with your question. It actually seems like there should be an easier way to do this, but try this and let us know if it works.
If it does work, be aware that one drawback of this method is that someone could disable the call forwarding on busy by dialing *61, or change it by dialing *60. To avoid that possibility, you could go into Star Code Profile A and find these two entries:
*60, Cfwd Busy, coll($Cfbn), set($Cfb,1)
*61, Disable Cfwd Busy, set($Cfb, 0)
Make sure the two checkboxes at the right hand side of the page (under Device Default and OBiTALK Settings) are unchecked next to those two lines, then just erase the contents of those fields and submit the page. If you ever want them back, just recheck the "OBiTalk Settings" checkbox on both lines and submit the page again.
One other thought that occurs to me is you MIGHT have to go into PHONE 1 and uncheck the box next to CallWaitingEnable,
or dial *57 from PHONE 1 to disable Call Waiting. Otherwise the person talking on the first line might get a call waiting beep when the second call comes in. I don't know offhand which feature takes precedence - Call Waiting or Call Forward on Busy.