| 摘要 |
A motor driven automatic exposure determining device for a camera in which the motor is operated in forward or reverse direction from a single voltage source. In addition to driving an exposure control element, such as a shutter speed control mechanism or a diaphragm aperture control mechanism, the motor drives a variable impedance of a bridge circuit for balancing the bridge circuit. Another impedance of the bridge circuit is a photoelectric element responsive to light from the scene to be photographed. A transistor switching circuit, comprising four transistors, is employed to control the connection of the motor terminals to the terminals of the single voltage source by providing circuits for energizing the motor for forward or reverse rotation depending upon which of two pairs of the transistors is rendered conductive by a detecting transistor circuit responsive to bridge unbalance and to the direction of unbalance. By a unique interconnection of the detecting circuit and the switching circuit, a single transistor of the detecting circuit renders a pair of transistors of the switching circuit conductive simultaneously and with low power consumption.
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