If you connect your OBi110 Line Port (FXO) to your POTs line, any calls that come in on the Land Line (POTs) phone number will ring the phone connected to Phone Port of the OBi110. Also 911 Calls will be routed to use the Land Line. Incoming calls via your VoIP service will come in on the provisioned Service Provider Port. You can choose to have outgoing calls go out on either via the Land Line or by your VoIP service provider provisioned on SP1 (or on SP2).
If you use OBiTalk to Administer your OBi110, you can setup the Outgoing Call default that will be used for all dialed (outgoing) calls. If you don't use OBiTalk, you can use the Web Administration interface to configure the default outgoing call port.
You can override the default for outgoing calls by dialing **1, **2 or **8 before dialing the number.
1) **1 + <called phone number) will dial out on SP1.
2) **2 + <called phone number) will dial out on SP2 (if equipped).
3) **8 + <called phone number) will dial out on the POTs (Land-line) Port.
4) # will also access the Land-line Port.
OBi110 Detailed Technical Specifications.
http://www.obihai.com/docs/OBi110DS.pdf