Patent ID: 7330135

Claim:
A method for reading out keys of a keyboard, in particular a keyboard of an automatic teller machine, said keys being arranged according to a row and column set-up of a matrix, wherein a first scanning pattern for reading out said keys is applied to said keyboard, said method comprises a first series of steps consisting of: (a) randomly generating said first scanning pattern, which comprises for each of said rows and columns a first read-out value to be applied onto said row respectively said column; (b) applying said first scanning pattern onto said rows and columns during at least a first minimum time period; (c) applying a verification routine in order to determine if the actual values of each row and column correspond to those applied by the first scanning pattern and to identify those rows and columns for which the actual value does not correspond to the one applied by the first pattern, (d) repeating, after said first time period has lapsed, said first series of steps if no rows and columns have been identified by said verification routine; characterised in that said method further comprises; (e) temporarily storing a pointer pointing to said rows and columns identified during said verification routine; (f) applying a second series of steps which is started after storing said pointer, said second series of steps comprises: (g) randomly generating, after said first time period has lapsed, a second scanning pattern comprising for at least each of said rows and columns indicated by said pointer a second read-out value to be applied onto said rows and columns; (h) applying said second scanning pattern to said rows and columns during at least a second minimum time period; (i) monitoring said identified rows and columns by using said second pattern in order to confirm as activated keys those keys located on said identified rows and columns.