发明授权
- 专利标题: Transparent calculator for overhead projection
- 专利标题(中): 用于架空投影的透明计算器
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申请号: US400158申请日: 1989-08-28
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公开(公告)号: US5035502A公开(公告)日: 1991-07-30
- 发明人: William T. Stokes
- 申请人: William T. Stokes
- 专利权人: Stokes William T
- 当前专利权人: Stokes William T
- 主分类号: G03B21/132
- IPC分类号: G03B21/132 ; G06F15/02 ; G09B5/00
摘要:
A hand-held calculator has a transparent window carrying a liquid crystal display as well as transparent number and function key locations such that when placed on an overhead projector, the calculator can be used to demonstrate to a classroom of students all operations performed in a sequence of mathematical operations. The plastic casing of the calculator has one or more small holes passing through the casing at corners. Another feature of the calculator is an improved keyboard of relatively small domain size for each key, with a spacer grid on the back surface of the keyboard membrane panel overlay element, effective to provide pressure isolation of an active key from adjacent keys and also to prevent other pressures on the keyboard from causing mistaken entries. A further feature of the calculator is a protrusion or foot at each corner of the back of the calculator casing. Finally, the calculator in a preferred embodiment has a plurality of different background colors for different groups of the transparent function keys.
公开/授权文献
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