All you need is a classic analog phone and an ATA box. Analog Telephone Adaptor basically translates your phone into TCP/IP and puts your on the Net! 

You create an account on  https://pots-box.org/  and list the lines you have. PotsBox will give you the SIP credentials and you'll see your phones register. 

Now, you can pick up and dial the Operator, find services in a Yellow Pages library and dial other phones. Easy!