Push button telephone keyboard with two key types only - each with three teeth of different length operating three sets of bars

摘要

The pushbutton telephone keyboard has each of its keys provided with three operating teeth of different lengths and operating a horizontal, a vertical and common bar. The bars are arranged in superimposed but different planes and operate the supply and selection contacts of the electronic selection control circuit. The keys are of only two types: these types differ in that the longer and shorter teeth are interchanged. The common bar lies in a plane above the horizontal bar which is in turn above the vertical bar.