When I was in the corporate world, "9" was a common prefix to get an outside Line, so that is what I use.
OBi???:
Physical Interfaces -> Phone Port -> DigitMap
Add AFTER the beginning parenthesis: 9xxxxxxxxxx|
Physical Interfaces -> Phone Port -> OutboundCallRoute
Add to the beginning: {(<123456789*>9xxxxxxxxxx):pp},
Change 123456789 to the OBi number of the OBi110
OBi110:
Voice Services -> OBiTalk Service -> InboundCallRoute:
{987654321>(<9:1>xxxxxxxxxx):li},{ph}
Change 987654321 to the OBi number of the OBi???
Use OBi Expert to make these changes.
The above will send a 10 digit number prefixed with a "9" to the OBi110. The OBi110 will change the prefix to "1" and route the call to Line. You might have to change this depending on your requirements.