| 摘要 |
The letter box has a security screen (B) which isolates the depositing (A) and storage parts (C). It has four fixed sides (1, 2) and two mobile sides (3, 4) which pivot round an axle (5) to close or open the top and base of the box. A counterweight (7) keeps the box closed when the screen is at rest. Objects can be deposited in the centre part of the screen when the front side (3) is open and the base is closed. The objects are transferred to the storage part when the front of the screen is closed and its base is open.
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