Exposure control device for photographic cameras

Claim 1

A photographic camera having a shutter, a shutter opening mechanism, a shutter closing mechanism, an exposure control device actuated by the charged state of an RC circuit having a charging capacitor (2) and a photoconductive cell (1) connected in series therein, said photoconductive cell exposed during film exposure, a limit threshold switch )14) connected in series with said RC circuit, an output circuit connected in series with said limit switch, a first electromagnet inserted in series with said output circuit, said first electromagnet actuating said shutter closing mechanism, means for digital counting (3,4) connected in series with said limit switch and said first electromagnet (9) for selecting film sensitivity, said means for digital counting having outputs selectively connectable in series with a plurality of circuit elements (7,10,11) which vary the current supply to said first electromagnet (9) and simultaneously short circuit said charging capacitor (2) of the RC circuit, said means for digital counting comprising a plurality of digital counters (3,4) connected in series, a further digital counter (6a) connected in series between said digital counters and said circuit elements for the feeding of selected additional exposure constants, said circuit elements comprising a flip-flop (7) with two outputs (16,17), said first electromagnet (9) which closes the shutter being connected to one of said outputs (17) thereof in series with a first transistor switch (8), and a second transistor switch (11) short circuiting said charging capacitor (2) being connected in series with the other output (16) of said flip-flop, in series with a NAND gate (10) additionally controlled by the limit switch.