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).
Tables specifying the operational positions, component gaps, and depression formulas for duplex push button switches.
| Identifier | ExFiles\Box 64\3\ scan0274 | |
| Date | 25th June 1926 | |
| x7610.ps. 25.6.26. 7c/c DUPLEX PUSH BUTTON SWITCH TABLES. Position. | Button depression. | Copper gap. | Carbon gap. Off. | A | B | Ψ (B-C) Carbons in contact. | A + (B-C)/θ | C | O Coppers in contact. | A + B/θ | O | O Specified gaps. Position. | Button depression. | Copper gap. | Carbon gap. Off. | A + .000 | .035 +5 -3 | .019 +13 -8 Carbons in contact. | A + .011 +7 -4 | .020 +3 -5 | O Coppers in contact. | A + .025 +4 -2 | O | O where A = initial button depression. EFC/HEW. | ||