Importance

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Abstract

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 conducted, 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.

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First Claim