| 摘要 |
A device containing an optical window, which prior to activation is covered with a cover having a reflective surface. Behind the window within the device is a light emitter, preferably infra-red light, and preferably an infra-red phototransistor. The device contains a detector such as a microprocessor which can detect the presence of the cover by periodically activating the emitter and sensing the level of light reflected from the cover by means of the signal detected by the detector. The device is activated when there is no detection of the cover usually by activation of the operating software. |
