If you want all incoming calls on the LINE Port to go to the Auto Attendant, set:
Physical Interfaces -> LINE Port -> InboundCallRoute : aa
and (optionally) set an Auto Attendant PIN at:
Voice Services -> Auto Attendant -> UsePIN : (checked)
Voice Services -> Auto Attendant -> PIN1 : (must be all digits)
If you want only selected incoming callers on the LINE Port to go to the Auto Attendant and all others to ring the OBi phone, set:
Physical Interfaces -> LINE Port -> InboundCallRoute : {(Mcot):aa},{ph}
User Settings -> User Defined Digit Maps -> User Defined Digit MapX:
Label : cot
DigitMap : (aaaaaaaaaaa|bbbbbbbbbbb|ccccccccccc)
where aaaaaaaaaaa, bbbbbbbbbbb, and ccccccccccc are the CallerID's of callers who are to go to the Auto Attendant.
Be aware that due to a bug in the OBi firmware, you cannot use *78 (Do Not Disturb) to silence incoming calls destined for the OBi's phone, nor can you use *72 (Call Forward All) to forward incoming calls destined for the OBi's phone. If either of these features is used, all InboundCallRoute processing stops on the SP1, SP2, and LINE Port trunks, breaking all your rules to send certain callers to the Auto Attendant and any other techniques utilizing similar InboundCallRoute processing on these trunks. Even though correcting the problem is extremely simple, I've been informed by Obihai they will not be fixing this bug.