On Sun, 2004-08-08 at 10:51, Tore S Bekkedal wrote: Cool find! Here's the cogent text from that page, though this vintage is too old for me to have worked on, it brings back memories of weird interfaces: "... The 407 [peripheral to 709x] also had the closest thing ... to a time-of-day clock. It was a mechanical clock built into the 407 and counted 100ths of a minute. The 709x would interrogate the clock at the start and end of each job. Interrogating it was kind of interesting, because it involved printing the clock value on the printer, terminating the cycle before it actually made a mark on the paper, and then using the "echo checking" feature of the printer to fetch the actual value. Echo checking was a way for the program to make sure that the mechanical printer had actually printed the correct digit on the paper. The side effect of this is that if the program running interrogated the clock (say, with a call from Fortran, or if the operating system did it between steps of a job), the printer made a funny noise -- like printing, but not quite." Not unlike reading multiplexed seven-segment output from a watch chip, no?!