This document contains the technical description of the transmission technique, coding language, and user interface for one-way broadcast teletext-service applications in North America. The first seven chapters in this specification generally correspond to the seven layers in the Open Systems Interconnection (OSI) basic reference model (chapter 1 corresponds to layer 1, etc.), however not all parts of each chapter necessarily correspond to the appropriate layer. A fundamental concept embodied in this teletext standard is that of maintaining the distinction between the means of transporting the data and the coding of the teletext message. The data transmission system does not impose any restriction on the data which can be transmitted. Similarly, the coding language is independent of the transmission technique. For example, the presentation technique of this coding language may be used with conventional modems on a switched telephone network.