Apparatus and method for analyzing and encoding graphical data into a serial character stream for transmission over a communications system to a remote data terminal where the character stream is decoded to generate a high resolution graphical display of the data. The graphical display is generated on a teletypewriter which has been modified to permit relatively small, positive and negative incremental movements of the typewriter type carriage and platen in their respective horizontal and vertical directions. The coding scheme includes analyzing the graphical data on an incremental point-to-point basis to determine the quadrant of movement to the next point, the horizontal and vertical increments, and the symbol to be printed. The data is also analyzed to detect information which is invariable over a plurality of points and such information is commanded to be stored in the receiving remote data terminal. Thereafter, only variable information is transmitted to the remote terminal until one of the invariable items of information changes. Alternate apparatus and methods are disclosed for further reduction of the transmission of invariable information and for suppressing the printing of symbols which contain graphing information.
