US Patent 7541554 Key structure

A key structure comprises a membrane circuit, a substrate, a cover and a press element. The membrane circuit comprises at least one first signal generator and a second signal generator. The substrate is disposed below the membrane circuit to support the membrane circuit. The cover comprises a body and at least one protrusion, wherein the protrusion is disposed on the body corresponding to the first signal generator. The press element is disposed on the second signal generator, wherein when force is applied on the cover, the protrusion presses the first signal generator.