a first protective layer receiving a pressing force;

a second protective layer, wherein the second protective layer and the first protective layer are combined with each other and collaboratively formed as a covering structure;

a first conductive layer installed on an inner side of the first protective layer;

a second conductive layer installed on an inner side of the second protective layer, wherein the second conductive layer is aligned with the first conductive layer; and

a force-sensitive layer installed on the first conductive layer or the second conductive layer, wherein when the first protective layer receives the pressing force, an electric connection between the first conductive layer and the second conductive layer is established, and the force-sensitive layer generates an analog sensing signal in response to the pressing force, wherein when a magnitude of the pressing force is changed, the analog sensing signal is correspondingly changed according to an impedance change of the force-sensitive layer,

wherein a keycap and a pressing element are located outside the first protective layer, wherein when the keycap is pressed, the pressing force is transmitted through the keycap, wherein the pressing element is arranged between the keycap and the first protective layer, the pressing element is subjected to compressible deformation to press the first protective layer in response to the pressing force, and the pressing element is restored to an original shape after the pressing force is eliminated,

wherein a shape and a location of the pressing element respectively match a shape and a location of the force-sensitive layer.