Patent ID: 7339499
Filing Date: 2008-03-04
Classification: G06F,H01H,H03M

Abstract:
1. Keypad apparatus for registering signals corresponding to data that a user enters by pressure, comprising: a surface extending in two dimensions; first and second sets of impedance elements, the elements of each set being connected in series through respective interconnections; reference signal means for applying first and second reference signals across said first and second sets of impedance elements respectively; and an array of discrete key elements juxtaposed with said surface and selectively actuable by user pressure on said key elements to make or break connections through corresponding contact elements between a respective pair of said interconnections, one from said first set of impedance elements and one from said second set of impedance elements, characterised by said reference signal means is arranged to apply said reference signals alternately across said first set and across said second set of impedance elements, so as to generate first and second output signals that together are a corresponding combination of said first and second reference signals that is unique to the actuated key element or key elements, and output means responsive to said output signals, said output means comprising analogue-to-digital converter means common to said first and second output signals, wherein said analogue-to-digital converter means is responsive to analogue values of said output signals to generate digital output signals.