Method 1: using cordless phone set:
Connects your cordless phone base to cell2jack then all cordless handset in different room will work.

Method 2: using multiple Cell2Jacks:
Your cellphone can connect to multiple Cell2Jack. You can put a Cell2jack which connects to your home phone in each room

Method 3: Connects via Wall phone socket:
Not recommended if you are not sure it is clean behind your wall phone socket.
Please take a look below link to ensure your wall phone socket is clean.
​Wall phone socket