Before photocopiers & laser printers were ubiquitious, there were many curious methods of duplication. See: https://en.wikipedia.org/wiki/List_of_duplicating_processes 1) if you have a paper copy that's a B&W negative, it is probably a Photostat. I found several photostats in my dad's papers. https://en.wikipedia.org/wiki/Photostat_machine Description Both Rectigraph and Photostat machines consisted of a large camera ... After a 10-second exposure, the paper was directed to developing and fixing baths, then either air- or machine-dried. Since the print was directly exposed, without the use of an intermediate film, the result was a negative print. 2) I once salvaged a Thermofax machine. It was a box of BRIGHT lamps and a heated roller. No chemicals required. https://en.wikipedia.org/wiki/Thermofax 3) I once had a little darkroom kit with a contact printer which was a tin box with a light bulb inside, a glass top with hinged top. The paper was developed by inserting it into a plastic gadget where a crank turned rollers (via gears) dunking the paper into 3 consecutive chemical trays. 4) The way these relate to computers & electronics: several of these processes were used for chart recorders and "oscillographs" (oscilloscope where a light beam was bounced by moving mirrors onto a screen, or film). High resolution charter recorders avoided pen lag & overshoot by using a galvanometer and light beam onto light sensitive paper. I think HP used IR onto heat-sensitive paper similar to today's receipt paper. -- jeff jonas