Fremgangsmåte for identifisering av aktivert tast i en ikke-kodet tastatur-matrise, samt krets for iverksettelse av fremgangsmåten

The present invention relates to a method for distorting and the circuit for carrying out this method. The method of distorting consists: a) in output-connecting all the rows and columns of the keyboard to the outputs of a first register (160) of a parallel input-output interface (16) by way of a circuit (163, 166, 164); b) in connecting all the rows and columns of the keyboard to the inputs of the second register (167) of the input-output interface; c) in randomly drawing the order in which the outputs are to be scanned; d) in setting at least one of the outputs to "1" and in observing whether one of the corresponding inputs is at "1"; e) in the contrary case, in scanning each of the remaining lines one by one while setting it to "1" until the associated input is at the value "1"; f) in repeating steps d) and e) to determine the column or respectively the line corresponding to the depressed key of the keyboard.