A switch unit has a display part that displays an image in at least one input area, a substrate provided above the display part, the substrate having a contact, and at least one substrate opening configured to allow the image in the at least one input area to be viewed from above, an operating button case that covers the substrate, having at least one button case opening, at least one operating button that has translucency, and that is freely pressed down through the at least one button case opening of the operating button case and causes conduction of the contact by being pressed down, light sources mounted on the substrate, that illuminate an area surrounding the at least one operating button, and a light transmissive water-proof sheet made of an elastic member.

A composite function keyboard circuit includes a first matrix circuit, a first bias resistor group, a second matrix circuit, a second bias resistor group and a controller. Each switch unit in the first matrix circuit is an ink-type force sensing switch. A resistance of the ink-type force sensing switch is variable according to a pressing mode of a keypress action. An electrical connection path is formed between the ink-type force sensing switch and the corresponding bias resistor of the second bias resistor group. When the ink-type force sensing switch is electrically conductive, a divided sensing voltage is generated by the electrical connection path, and the controller generates a corresponding key control instruction according to a level of the divided sensing voltage. Furthermore, the cooperation of the first matrix circuit and the first bias resistor group can achieve a ghost key preventing function.

A composite function keyboard circuit includes a first matrix circuit, a first bias resistor group, a second matrix circuit, a second bias resistor group and a controller. Each switch unit in the first matrix circuit is an ink-type force sensing switch. A resistance of the ink-type force sensing switch is variable according to a pressing mode of a keypress action. An electrical connection path is formed between the ink-type force sensing switch and the corresponding bias resistor of the second bias resistor group. When the ink-type force sensing switch is electrically conductive, a divided sensing voltage is generated by the electrical connection path, and the controller generates a corresponding key control instruction according to a level of the divided sensing voltage. Furthermore, the cooperation of the first matrix circuit and the first bias resistor group can achieve a ghost key preventing function.