If the Internet goes down at my home, can I still make calls with the OBi?
No. However, if you have an OBi110, you can make calls as long as you have an active telephone service connected to the LINE port of the OBi device and this service is not dependent on the Internet for its operation, e.g. a service from your local telco / incumbent phone company.
About the OBi
6001 America Center Dr
San Jose, CA 95002