Welcome to the forum!
By default the OBi110 uses POTS for its Primary Line. This means no extra codes are needed to dial out to POTS. They would dial **9 followed by your OBi number to call you via OBiTALK.
The not so good news is that the DigitMaps are set to match North American defaults. If a number is not matched, it will be sent out to POTS, but the OBi will wait ten seconds to see if the user has finished dialling. This is obviously very bad news for emergency calls.
If you can supply some info on what your in-laws normally dial, then we can help to craft DigitMaps to suit. Tell us about emergency numbers, are local numbers seven digits starting with x, national calls are ten/eleven digits starting with xx, any special codes etc?