Patent ID: 8258985

Claim:
A scanning circuit used in a keyboard with a plurality of keys, the scanning circuit comprising: n input ports K 1 ˜Kn, arranged in n rows L 1 ˜Ln, wherein n is a natural number which is no less than 3; and m−2 output ports W 2 ˜W(m−1), arranged in m columns P 1 ˜Pm, wherein m is a natural number which is no less than 3; wherein the n rows and the m columns define a switch matrix comprising n*m switches, an ends of the switches in the same row are electrically connected to one of the n input ports K 1 ˜Kn, respectively, the ends of the switches in the column P 1 are connected to ground, the ends of the switches in the same column of the columns P 2 ˜P(m−1) are electrically connected to a power supply VCC via resistors R 2 ˜R(m−1) and the m−2 output ports W 2 ˜W(m−1), respectively, the ends of the switches in the columns Pm are electrically connected to ground via a resistor Rs and the power supply VCC via the resistors R 2 ˜R(m−1) and diodes D 2 ˜D(m−1), respectively, the cathodes of the m−2 diodes D 2 ˜D(m−1) are electrically connected to the resistor Rs, and the anodes of the m−2 diodes D 2 ˜D(m−1) are electrically connected to the power supply VCC via the resistors R 2 ˜R(m−1), respectively.