Xerox 420

The 420. Mechanically as the 914 but with Differential Billing. The Platen Cover, cheat switch is in the triangular hinge at the left of the stainless steel handle. The billing meters are under the lower, front cover, to the left of the paper-tray.

Internally identical to the 914, in every way, this was a marketing modification, carried out in the field or at refurbishment workshops. No 420s were ever factory produced. The idea was to encourage volume usage, through the use of Differential Billing. The Mod. Kit contained a new Copy Meter, with three windows, a new platen handle assembly, complete with drilling template, and a wiring loom.

The little, L shaped handle was removed from the platen cover and replaced with an assembly comprising a stainless steel, telescopic tube, terminating in a substantial hinge assy. which needed to be bolted to the top deck, slightly to the left of the platen cover. Inside this hinge was a mercury switch to detect whether the platen cover was fully closed - or not!

The triple meter assy. could be set to suit the marketing requirements. The top, No.1 meter recorded the expensive, Top Rate, copies. The No.2 meter recorded the cheaper rate copies. Typically, copies 1-5 on 1 and 6 and upwards on 2. The No.3 meter remained the Total Usage counter. As long as the original was not changed, any further copies dialled-up would be at the cheaper rate. Lifting the platen cover would cause the mercury 'cheat' switch to reset the system to the expensive tariff.

Thanks to Stuart Yearsley for providing this information