From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
The measurements and tolerances for a push-button switch.
| Identifier | ExFiles\Box 34\3\ Scan047 | |
| Date | 23th September 1919 | |
| To etc. for Mr. Brock from BY/HBO. BY/HBO4/DW.23/9/19. C. to EFC. RE PUSH BUTTON SWITCH - SEC. 7210. Further to our memo' BY/HBO3/DW.18/9/19.- POSITION | A CARBON GAP. | B COPPER GAP. | C BUTTON DEPRESSION. OFF | .050 +10 -10 | .064 +7 -7 | 0 Carbon just in Contact. | 0 | .033 +7 -7 | .024 +5 -5 Copper just in Contact. | 0 | 0 | .051 +6 -6 Copper with .015 +5 -5 Depression. | 0 | 0 | .063 +6 -6 BY/HBO. | ||