Patent ID: 7375655

Claim:
A keyboard without ghost keys comprising a circuit which has a microprocessor in which a plurality of I/O lines form a keyboard scanning matrix, two of the I/O lines being crossed to define a plurality of signal switches, the microprocessor being electrically connected to a primary level resistance and a reference potential to determine an ON condition of the signal switches, wherein: the signal switches are electrically connected to at least one secondary level resistance which is electrically connected to the primary level resistance in a serial manner and coupled in a parallel manner with another secondary level resistance on a neighboring parallel I/O line, depressing any three signal switches of four signal switches formed by vertical and parallel I/O lines generating a toggle key signal, the primary level resistance and the secondary level resistance being connected in a serial and parallel manner to form a new level resistance to eliminate the ghost keys; wherein the secondary level resistances are located in front of and behind a conductive point of the signal switches to connect to the primary level resistance in a serial manner.