Security membrane keyboard

摘要

A security membrane keyboard is presented. In the usual construction of membrane keyboards comprising base, lower contact membrane, spacing membrane, upper contact membrane and design membrane there is inserted above the upper contact membrane an additional sturdy metal foil with resilient properties. This has the effect that there cannot occur any permanent deformations, attributable to finger force, of the keyboard surface, which could divulge the code key to unauthorised persons. In addition, this sturdy metal foil lends the keyboard a high level of resistance to violent attacks, for example to attempts to scratch or cut it. The insertion of raised elements between the keyboard base and the lower contact membrane achieves the effect that, if pressure is applied from above, all the membrane layers can go down over wide areas with a large radius of curvature and that, at the same time, the lower contact membrane is deformed to enter into a clearance of the spacing membrane until contact is made. This effect has the result that, in spite of the sturdy metal foil used, the exertion of little force suffices to achieve a deformation until contact is made when a key is depressed. <IMAGE>