| 摘要 |
PURPOSE:To select automatically an optimum speed changing ratio in accordance with the conditions of speed changing ratios on the high speed and low speed sides by switching the turning direction of a motor at the reduction of the turning speed of the motor and selecting a driving string having the speed changing ratio of the low speed side. CONSTITUTION:At the reduction of power supply voltage or the delay of the rotation of the motor M under a low temperature, the ON/OFF period of a switch SW2 is expanded during the output of a high level signal from a counter 23 and a counter 26 can not count up to ''5''. Therefore, the output of the counter 26 is kept at a low level signal and the outputs of AND gates 30, 31 are turned to a low level signal and a high level signal respectively. When the output of the gate 31 is turned to the high level signal, TRs 36, 39 are turned on through resistors 32, 35 respectively and current shown by an arrow of a solid array is made to flow into the motor M, so that the motor M starts to rotate forward. The transmission of driving force in both forward and backward rotation is made the same in accordance with the number of arrayed gears and the optimum speed changing ratio transmitted to the camera side is automatically selected. |
