| 摘要 |
PURPOSE:To eliminate malfunction owing to a stained element providing a means which monitors the voltage from the element in the state of absence of paper on a photoreceptor and stores the same when said voltage drops lower than the prescribed voltage and a switching means which operates so as to decrease the reference voltage of a comparator when said state is stored in this storage means. CONSTITUTION:The output voltage Vi from an amplifier 6 is inputted to the 2nd comparator 10, where the voltage Vi is compared with the 2nd reference voltage VR2. The comparator 10 is so arranged that its output does not go to a high level unless the voltage Vi rises higher than the voltage VR2. The output of the comparator 10 is inputted to the terminal D of a D type flip-flop 11. On the other hand, the clock signal S generated when no paper is fed to the photoreceptor is fed to the clock terminal T of the flip-flop 11. With such constitution, the flip-flop 11 is remained unset as far as the voltage Vi is at the level higher than the voltage VR2. |
