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 126
carelessness, are overcomeby the Controlled-Key, which, if not givenits full down-stroke, causes the keys in all theother columns to lock up instantly ; and whenthe operator goes on to the next key after sucha misoperation, he finds it will not godown. On looking at the answer register hesees in… … Fig. 37.—Interference Guard, andCushioned Key-tops.
