| 摘要 |
The disclosed exemplification of the present invention is a film position and break detector for use with a motion picture projector and the like. An opaque magnetic material in the form of a strip extends along each longitudinal edge of the film and preferably contains information relating to film speed. A portion of one strip is removed at the beginning end of the film and a portion of the other strip is removed at the finish end of the film leaving transparent portions of the film exposed. A pair of light sources are mounted on one side of the prescribed path of film travel and are positioned to illuminate a respective magnetic strip. A pair of light sensing diodes are mounted on the opposite side of the prescribed path of film travel and are positioned to be illuminated from a corresponding light source in the absence of any magnetic strip interposed therebetween. A circuit is responsive to the conduction of one light sensing diode to actuate the film translating mechanism of the projector to drive the film in one direction and is responsive to the conduction of the other light sensing diode to actuate the translating mechanism to drive the film in the opposite direction. The circuit is further responsive to the conduction of both light sensing diodes to de-energize the film translating mechanism.
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