| 摘要 |
A film cassette comprises a film spool supported within a lighttight shell for rotation in an unwinding direction to thrust a filmstrip coiled about the spool to the exterior of the shell and for rotation in a winding direction to return the filmstrip to the interior of the shell. According to the invention, a locking device is connected to the spool and the shell for preventing rotation of the spool in the unwinding direction, and is enabled for such purpose in response to rotation of the spool in the winding direction. This prevents a photographer from reusing the cassette in a camera after the filmstrip is fully exposed. The locking device can be manually defeated to reuse the cassette in the camera when the filmstrip is only partly exposed.
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