Make the home phone line higher priority than any ongoing SIP/VoIP call ?

[extraordinary]

Hi-
I use phonerlite+obiapp to make calls from my PC, but, I want to disconnect any ongoing calls if someone in the house picks up the phone to make a call (higher priority to people in the house).

The default behavior is to hear a prompt asking the user to check the obi configuration. So even a 911 call can not go through.

How do I fix this ?

Thanks!