DocuTech is the name given to a line of electronic production-publishing systems produced by Xerox Corporation. It allowed paper documents to be scanned, electronically edited, and then printed on demand. DocuTech systems were the last known to use the XNS protocol for networking. The very first DocuTech system, known as the DocuTech Production Publisher was announced on October 2, 1990. Its 135 page-per minute, black and white, xerographic print engine and attached finisher module were largely based on ones previously developed for the Xerox 5090 Duplicator system (announced by Xerox in 1988). However, image generation in the DocuTech was performed using a digitally driven, dual-beam, Laser ROS (Raster Output Scanner) rather than by the light-lens optics and exposure lamps found in the "analog" 5090 system. The system's scanner module allowed document scanning in a number of modes including manually from the platen or automatically using a 23 page-per-minute recirculating document feeder. The scanner also had a semi-automatic side feeder which could be used to scan large originals and computer fan-fold (CFF) input. The entire system was controlled by an electronic sub-system (ESS) of a proprietary Xerox design. The ESS incorporated a large number of Xerox proprietary Mesa processors which were specifically designed for high-speed image processing, 32 MegaBytes of RAM, I/O control interfaces for communicating with the Printer and Scanner modules, as well as 3 disk drives which contained system software and space for storing images (including those for saved jobs). With its ability to digitally scan, edit and store documents for later retrieval, and also its ability to output stitched or tape-bound books, the DocuTech Production Publisher was arguably the first fully integrated "print-on-demand" publishing system. In fact, the Xerox DocuTech line of publishing systems is largely credited with establishing the "print-on-demand" industry. In late 1991, Xerox re-branded the original DocuTech Production Publisher as the DocuTech Production Publisher Model 135 (DT135). This was done to distinguish it from the DocuTech Production Publisher Model 90 which the company anticipated announcing in 1992. The model numbers were chosen to reflect the page-per-minute print speeds of the two models. The controller and scanner were common to both models, but the Model 90 used a different print engine based on one developed for the previously announced Xerox 4090 printer. The original DocuTech Production Publisher was capable of scanning and then printing black-and-white pages at up to 135 pages per minutes (for letter or