Patent ID: 7978098

Claim:
A key input device identifying a key used to make an input, out of a plurality of keys, comprising: a control unit; a plurality of resistor string units each configured to generate a resistance value corresponding to an input, the plurality of resistor string units being connected to each other at a connection node at one end of the plurality of resistor string units; and a selection unit connected to said plurality of resistor string units, and electrically connecting one of said plurality of resistor string units between a first potential and a second potential in accordance with a selection command from said control unit, wherein each of the plurality of keys is uniquely assigned to any of said plurality of resistor string units, said control unit identifies the key used to make the input, based on a voltage value appearing at said connection node and said selection command provided to said selection unit, and said control unit outputs said selection command such that one of said plurality of resistor string units is sequentially selected to be electrically connected between said first potential and said second potential.