1. Field of the Invention
The invention relates in general to a signal input apparatus, and more particularly to a signal input apparatus having alternative power supply while the battery is exhausted
2. Description of the Related Art
Computer mouse is a signal input apparatus of a computer, especially being a pointing device for controlling the displacement of the cursor on screen. Conventionally, computer mouse is classified as an optical mouse and a mechanical mouse. The mechanical mouse controls the displacement of the cursor according to the input signal produced in accordance with the relative position of the rolling ball. Compared to the mechanical mouse, the optical mouse detects the relative movement of the mouse by an optical sensor and the optical sensor includes a light emitting diode (LED), lens and sensing IC. The sensing IC is preferably an IC of Agilent Technologies Ltd, the model No. of which is ADNS-2610 (referring to the U.S. Pat. No. 6,433,780).
Moreover, it brings more convenience to users that the computer mouse communicates with computer by wireless technique. When a computer and a projector are common applications in business, a wireless computer mouse allows a speaker to control the computer and move simultaneously during presentation.
However, a wireless computer mouse is driven by power of a battery, and the wireless computer mouse cannot be driven when the power of the battery is exhausted. Also, a pointing stick or a laser pen is required for the speaker to guide listeners' sight during presentation, but it is not easy for the speaker to hold a wireless computer mouse and a laser pen in one hand.