| 摘要 |
<p>A double exposure warning for a camera with a motor drive unit has two oscillator circuits (8,9) to generate a signal when the double exposure switch is operated. The signal can be an acoustic warning (10) or an optical flasher, the latter being used in churches, courts, lectures etc. for silent operation. The signal serves to prevent the user from taking double exposures through neglecting to switch off the facility at the end of a double exposure or sequence of them. The warning can be included in the motor drive. A unit in the camera body can be moved by a side switch slidable between end positions to allow usage of the double exposure model. A switch (S2) in the motor drive unit is simultaneously operated to activate the warning circuit (6) when the exposure button is pressed. Both oscillators (8,9) consist of a resistor (11,12), a capacitor (13,14) and a NAND gate (15,16) with Schmitt trigger inputs.</p> |
