Abstract: A telephone instrument includes a built-in modem device that is connected electrically to a telephone line and to a data network terminal. The modem device can be activated by the data network terminal to establish communication between the data network terminal and an Internet service provider through the telephone line in response to a request to access the Internet from the data network device. A signal coder/decoder in the telephone instrument permits conversion of an outgoing call signal that was picked-up by a handset unit into encoded outgoing call data having a call data format that conforms to voice communications protocol through the Internet service provider. The signal coder/decoder further permits conversion of encoded incoming call data generated by the data network device from an incoming network signal that was received from the Internet service provider into an incoming call signal to be reproduced by the handset unit.