New non-voice services (sometimes also called information services) and the possibilities of telecommunication networks to support them are described in this state-of-the-art review. It begins with a summary of the various data transmission techniques, which include several types of data transmission over the telephone network: general, telegraph multiplexers, data multiplexers, modems for leased circuit applications, and modems for the switched telephone network. Tables are used to list specific equipment and provide additional technical details. The second section covers data transmission over public data networks and discusses user classes of service (start-stop, synchronous, and packet-operating mode of the terminal), user facilities, and data communication policy. Necessary characteristics of text for communication service (Teletex) are outlined, and features of subscriber facsimile service and videotex service are discussed. (LMM)