| 摘要 |
PURPOSE:To prevent malfunction of an image printer by removing the noises on synchronous signal, and by generating a false synchronous signal by automatic oscillation at the time of non-input. CONSTITUTION:Input horizontal synchronous signal S1 triggers a single multi 3 through AND gate 2 to provide output Q to gate 2. Thus, output S3 of gate 2 becomes a noise removed signal. The synchronous signal S3 is provided to NOR gate 8 of oscillator 4. Output S8 of gate 8 is provided to EXOR gate together with system reset signal S7, and output S5 of gate 5 is inputted in retriggerable multi 6. Multi 6 outputs '0' for a little longer time than the horizontal synchronous period against start-input. Without input of synchronous signal in such a condition that signal S7 is on '1', output of multi 6 is provided to its input to make multi 6 perform its automatic oscillation. Output S5 of gate 5 becomes a false synchronous signal against deficiency of synchronous signal.
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