IBM 1627

The plotter fed a roll of paper with perforated edges over a drum with matching sprockets at the sides.

There were also commands to move the drum and pen together one step in the four diagonal directions.

A metal bar above the take-up reel allowed a finished plot to be torn off and removed.

The drum would then be advanced using the manual controls and the fresh paper end taped to the take-up reel.

A chart drive switch was provided to turn off the motorized paper supply and take-up reels for this purpose.

IBM 1620 data processing machine with IBM 1627 plotter, on display at the Seattle World's Fair, 1962
IBM 1627 drum plotter. Note pen assembly is missing.
Closeup of IBM 1627 drum plotter right side, showing controls for manually moving the drum.
A Calcomp 565 drum plotter, essentially the same as the 1627, with pen assembly.