Communication devices are tools used to send and receive messages. A payphone is a public TELEPHONE that requires coins or a prepaid card to make a call. A teletype is a device that sends and receives typed messages over a TELEPHONE line. A radiophone is a two-way RADIO that allows communication over long distances. An intercom is a device used for communication within a building or other enclosed area. A TELEPHONE is a device used to transmit sound, typically between two people. A RADIO is an electronic device that transmits and receives signals through the air. A PHONE is a device used to make and receive TELEPHONE calls. Tel is a shortened form of the word TELEPHONE.