A modem is a computer communication device that allows two computers to connect and exchange data over telephone lines. Email is another computer communication device that allows users to send messages electronically. A payphone is a public telephone that accepts coins or credit cards for payment. A teletype is a computer communication device that sends and receives typed messages over telephone lines. A radiophone is a communication device that transmits and receives voice messages over RADIO waves. RADIO is a communication device that transmits and receives sound signals through the air. Finally, a PHONE is a communication device that transmits and receives sound signals over telephone lines.