High Speed Line Printer

A Data Communication Historical Series

High Speed Line Printer (1962-1966; AUTODIN):

   This printer was designed for printing computer output and was connected to the computer through a device input-output channel (port). It was housed in a metal cabinet approximately 48” high X 36” wide X 30” deep, with a clear plastic cover. A paper tray for the unused and used paper was provided. It was an electrical-mechanical device utilizing transistorized logic.

 

   A complete line of information was printed, across the paper, containing all the necessary alphanumeric & special (symbol) characters during one rotation of the print drum. The width of the fan fold paper (sprocket fed) was similar to the sprocket fed computer printer paper used with present computer systems. The printer drum was of sufficient diameter to allow for individual rows of all alphanumeric characters and special symbols, I.E. a row of A', B's, C, 1's, etc across the full length of the drum. During one rotation of the drum a full line of data, across the paper, would be printed. The drum rotated continuously and when the print signal was triggered all A's across the paper, in the proper position, would be printed, then all B's, C's, etc followed by the numerals and special symbols, completing the full line of information in one rotation of the drum. The striking mechanism (print hammers) struck from underneath the paper, one for each character position on the drum. An inked soft roller was used to coat the up-lifted face of all the characters as the drum rotated. Also during this period in time the communication code sets provided for only upper case alpha characters, which was the type of data being processed by the computer that in turn was sending information to the printer for printing. Therefore it was only necessary for the printer to print upper case alpha characters. Refer to the illustration below.

 

   The timing of all functions was controlled by a spinning disk, with spaced timing holes, at the end of the drum. Light was used to shine through the holes and a light detector (photoelectric) controlled the necessary electronic timing and control signals, character buffering, start and stop print point for the drum, and paper feed timing.

 

   The printer was a high maintenance unit because it had many mechanical parts, sensitive electrical components and paper feed problems. These problems were created because the printer operated around 200 lines per minute. It kind of vibrated, rattled and shook itself to failure. It was also a problem in keeping the print lines nice and straight across the page.