Abstract: A decodable alphanumeric membrane switchcore (12, 12a, 12b,100) of at least 36 key cells (55,122) including spaced circuits (16,17;105,115) having row and column traces (20-34, 40-47,51;106,116) and key cell elements (37,38,49;80;107,117) printed with ink having a resisitivity of at least about 10 ohms per square per 0.001" of ink thickness and having at least one path defined by a row trace, column trace and a key cell that has a resistance greater than 10,000 ohms.

Abstract: In a capacitive switchcore of the type in which each key cell includes a contact switch in series with a key cell capacitor, an improvement is disclosed in which an intracell coactive loading capacitor is added to each key cell. The intracell coactive loading capacitor is connected between ground and the junction of the contact switch with the key cell capacitor. A matrix of key cells so formed is self-referencing, in that the need for a separate reference capacitor to load the sense line is eliminated. Instead, loading is provided intrinsically by the effect of the intracell coactive loading capacitors acting through multiple key cells connected to a sense line. A preferred embodiment in a capacitive membrane switchcore is described.

Abstract: A capacitance membrane switchcore (12,12a, 12b, 12c, 12c') including a first circuit (16, 16'), a second circuit (17,17') and a third circuit (49,49') in which intertrace coupling capacitors (58,58') couple conductive traces (40-47,135) of the second circuit (17,17') to conductive traces (51,51') of the third circuit (49,49'). Also disclosed is a capacitance membrane switchcore (12) including a first circuit (16) having at least one trace (65) with a first branch (65a) along a first surface (18a ) of a dielectric layer (18), a second branch (65b) along a second surface (18b) of the dielectric layer (18), an intratrace coupling capacitor (66,67) coupling the first branch (65a) to the second branch (65b), a third branch (65c) along the first surface (18a) of the dielectric layer (18), and an intratrace coupling capacitor (68,69) coupling the second branch (65b) to the third branch (65c).