Night operators were known to nap on top of the 1401s. When there was a need for more paper, they would be gently awakened. -rob On Tue, Mar 30, 2021 at 9:30 AM John P. Linderman wrote: > >> On Mon, Mar 29, 2021 at 5:16 PM Erik E. Fair >> wrote: >> > > >> Line printers are distinguished not by the width of the paper but by the >>> printer having enough print heads to print an entire line of output at a >>> time. That speed advantage made them the preferred output device for >>> many-page program listings, as opposed to a teleprinter terminals which >>> were more suitable for interactive computing. >>> >> There were originally two styles, the drum printers which DEC sold(e.g. >> LP20) and the chain printers that IBM offered (e.g. 1401). The drum had >> all the characters in each of the 132 columns (the upper case only printers >> were faster because the alphabet was on the drum in two places). The >> IBM ones has slugs on a rapidly spinning chain that was horizontal (and parallel) >> to the line being printed. The chain was easily replaceable by the >> operator - which was one of the duties we would have. When a user queued a >> printer a set of symbols (*i.e.* the chain of the needed output >> characters) was specified and the system queued it until the printer had >> been properly provisioned. For instance, CMU printed checks with a >> special chain and film ink, so once a night the operator would configure >> the printer, and tell the queue to print them). Some chains were faster >> than others, the standard one had N copies of each character. >> >> In common to both schemes is that each both styles had 132 hammers and >> when the proper character was in the position needed, the hammer fired to >> make an impression the ribbon on the paper, which was caused the noise >> people associated with computer printers. The high-end IBM 1401 had a >> hydraulic cover that came down over it and was controlled by the channel >> processor (it would auto-open when it needed to be serviced - like a new >> box of paper). >> >> This led to the "first commandment of fancy printers": Thou shalt not > leave thine coffee on top of the printer. -- jpl >