Automatic printer data stream language determination
 Printer (1) monitors current control language being interpreted for end of page and end of job codes, depending upon the language. Upon observing such commands, up to 500 bytes in buffer memory (19) are observed for command codes characteristic of specific languages. ASCII language is recognized by any one of several command codes, many of which have ESC. PostScript language is recognized by any one of several commands including the ASCII sequence of the percent sign. PCL4 or PCL5 and pen movement graphics languages are also recognized. Operator intervention and special coding defining the language are completely avoided. 
Lexmark International, Inc.
G G
G06K G06K
inventional additional
James D. Mark L. James F. David B. Stephen R.
Lewis Mayberry Webb Callister Troyer