| 摘要 |
<p>A box screwed to an up and over door contains a motor and the batteries to power the system. The cover is transparent to allow a lamp to illuminate the garage when the door is open. A window in the box aligns with a hole in the door to allow the optical signal from a vehicle to enter to open the door. A transparent plate allows the closing signal to enter to a detector. The motor pivots on a shaft to which a pulley is attached. A card passes over the pulley to a second pulley separated from it by an arm. A third pulley concentric with the second pulley, has a cord passing over it and which is attached to the garage walls. As the motor operates the pulley assembly traverses along this card to lift or lower the door.</p> |
