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Projection lamp control

Image Number 2 for United States Patent #4227781.

A cinematographic system including a programmable viewing apparatus by which an exposed photographic film strip in a multipurpose cassette may be processed, viewed by projection, and rewound, either entirely or for a selected film length for replay, without removal from the viewing apparatus. A control circuit is provided which continuously measures the position of the film strip in the cassette and precludes projection of the leading end of the film strip in response to signals received from the electronic logic system of the viewing apparatus. The signals condition the circuit to count in either the forward or reverse direction depending upon the direction of film strip movement. The count, which corresponds to the position of the film strip, is continuously displayed by the viewing apparatus. When the count is at or below a predetermined number corresponding to the length of the leading portion, the circuit will prevent the projection lamp from turning on during a project cycle. The circuit permits immediate projection lamp turn on during a project cycle whenever the count exceeds the predetermined number.

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