| 摘要 |
The device has an upper wall (3), and lower wall (2), where the lower wall includes a printed circuit board on its face. A grid is interposed between the walls and includes ring shaped units (40), where each unit is surmounted by a button (5). The lower wall is provided with emitting unit and the upper wall is provided with a receiving unit, where the emitting and receiving units measure the distance that separates the upper and lower walls to emit a signal when distance reaches a threshold value. |
