This was one of EAI's "Maintenance Series" manuals for the 12.848 Time Base Module of the EAI variplotter. It was published in November 1968 and gave detailed instructions and diagrams on how to maintain the time base module. It included "revision notice" in the front warning of a bug in the plotter.

This module was to be used only with the Model 99.730 Variplotter and the EAI 580 computer. The manual included a replacement part list and fold-out drawings of the schematics and wiring.

It's not a good sign when someone has written two phones numbers for EAI in the upper corner of the cover page of the manual. It looks like the manual wasn't as clear as one would hope and the user needed some further explanation.