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).
Table of measurements and test remarks for production push button switches.
| Identifier | ExFiles\Box 34\3\ Scan032 | |
| Date | 22th August 1919 | |
| X, 2641. 22.8.19. X+2641. - PRODUCTION PUSH BUTTON SWITCHES X.1627. [Left margin, vertical]: ADMIRALTY ORDER 33 A 12/7. D 8792/17. 1000 PADS Switch No. | Off-gaps (inches) | Copper gap, | First depression | Second depression | Remarks. | Carbon contacts. | Copper contacts. | carbons closed. | (carbon contact) | (copper contact). | ------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | .049 | | .030 | .025 | | TT 4 | 5 | 6 | .0195 | .043 | .030 | .010 | .033 | Returned first time. TT. | .027 | .048 | .030 | .014 | .037 | 7 | 8 | 9 | .027 | | .040 | .014 | | TT 10 | | ||