An input key assembly including: a keycap; a substrate; an elastic deformable shell-like structure disposed between the substrate and the keycap; and an optical sensing arrangement disposed on the substrate to transmit a light beam and sense an interruption to the light beam. The elastic deformable shell-like structure includes a peripheral base portion in abutment with the substrate; an apex portion in abutment with the keycap; and a plunger-like element extending away from underneath the apex portion, wherein a free-end of the plunger-like element is opaque. The elastic deformable shell-like structure and the optical sensing arrangement are arranged in a manner such that the free-end of the plunger-like element interrupts the light beam when the keycap is depressed to deform the elastic deformable shell-like structure for collapsing the apex portion relative to the peripheral base portion to move the plunger-like element along a longitudinal axis of the plunger-like element.

A switch device includes a circuit board, a coil structure, a lower cover, an upper cover, an elastic part, and a sliding part. The circuit board gas a through hole running through the circuit board. The coil structure is disposed on the circuit board and surrounds the through hole. The lower cover us located over the coil structure. The upper cover is disposed on the lower cover. The lower cover and the upper cover form an accommodating space. The elastic part is located in the accommodating space. The sliding part passes through an opening of the upper cover and is configured to slide relative to the lower cover along a direction. The sliding body is configured to drive the sliding part to pass through the through hole along the direction to generate a switch signal corresponding to an inductance variance of the coil structure.