Modern instruments and methods of calculation : a handbook of the Napier Tercentenary Exhibition (1914)
Horsburg, E. M. (Ellice Martin), Napier Tercentenary Exhibition (1914 : Edinburgh, Scotalnd) · London : G. Bell · leaf 125
Fig 36.—The Mechanism. to the inexperience of beginners and the carelessness of experienced operators—that the Controlled-Key was devised. This safeguard consists of :— 1. Interference guards at the side of the keytops to prevent accidentaldepression of a key at either side of the one being…
