IE32241B1 - Push button signalling - Google Patents

Abstract

1,198,308. Piezoelectric generators. STANDARD TELEPHONES & CABLES Ltd. 7 Dec., 1967, No. 55742/67. Heading H2A. [Also in Division H4] In a subscriber's V.F. keysender, each key is associated with a pair of piezo-electric elements and each element is connected to one of five monostable multivibrators whereby whenever a key is actuated a unique 2-out-of-5 U.F. signal of fixed duration is produced by the two energized multivibrators. As shown, depression of a push-button 15 is initially resisted by flexible limbs 19, 20, these limbs opening when sufficient pressure is exerted so as to allow a portion 16 of the spring-loaded key stem to impinge on piezo crystals 10, 11 and thus cause the latter to emit control signals to a pair of monostable multivibrators (Fig. 3, not shown). In another embodiment (Figs. 7-9, not shown) the keys are supported in resilient mountings and act upon bowed-springs when depressed. The bowedsprings may be formed integrally in a single sheet of springy material. The piezo elements may comprise a grid array of piezo strips, with push-buttons located at the cross-points (Figs. 6a, 6b, not shown). Fig. 10 (not shown) depicts the use of spring-loaded intermediate members which are arranged to impinge sharply on the piezo elements when their associated spring- loaded push-buttons are operated. In a similar arrangement (Fig. 12, not shown) the intermediate-members are initially made to touch the elements gently and then to move away from them rapidly when the push-buttons are actuated. The use of strips of piezo material which are supported at one or both ends so as to be bent by actuation of a push-button is mentioned with respect to Figs. 13 and 14 (not shown). [GB1198308A]