Abstract: A keyboard or switch matrix key closure validation device and method for a terminal, calculator, desktop computer, or the like is described. The keyboard or switch matrix consists of a matrix of momentary switching elements on "keys" whose number is larger than the number of rows or number of columns in the matrix. A microprocessor provides sequential scanning of the keys in the matrix. The microprocessor also provides detection of closed keys. Upon such detection the microprocessor performs a test for protection against pseudo keys, a debounce test and a detease test. Pseudo key protection is accomplished without each matrix key location having an associated isolation diode. Debounce testing is performed with an extendable bounce period.

Abstract: This invention relates to a keyboard switch or push button transducer for use in keyboards which makes use of the advantages of resistive and capacitive methods of closure. The switch element is comprised of a resilient conductive element attached to a pad of compressible foam mounted on the end of a key plunger. When the push button or switch plunger is depressed, the switch element is brought into contact with conductive elements etched on a printed circuit board. One of the conductive elements has a coating of dielectric material thereon, and the other conductive element has a raised conductive surface to contact the conductive elastomer sheet prior to the contact with the dielectric material. The insulated area forms a capacitance between the elastomer sheet and the conductive element or metallic pad on the printed circuit board, and the other area of conductor element, being uninsulated, makes a resistive contact with the elastomer.