| 摘要 |
<p>Visual aids are used involving film strips. There are several supplementary slides which are selectively displaceable in fornt of the window (10) of the fixed plate (2) of the viewing apparatus and superposed on the projected images of the film. The supplementary slides (14) are fixed around the periphery of a rotating disc (13) and the linear film can be fed by the rotation of the disc. In the case of more than one disc, the discs (13, 13') are mounted coaxially on cylindrical tubes (16, 17) but can be rotated independently. The movable plate (3) is pivotally attached (at 4) to the base support (1) and can be held perpendicular to the fixed plate (2) by a spring (5),.</p> |
