| 摘要 |
PURPOSE:To eliminate visual trouble of picture quality of a facsimile device by providing a hysteresis characteristic to the subtraction period of the detected number of changing points of a scanning line to prevent frequent switching of line density around a reference value of discrimination of line density. CONSTITUTION:The changing point of scanning line of an input data D is detected by a changing point detecting circuit 1 of an automatic line density discriminating circuit and applied to an up-down counter 2 as a clock UCK. Further, a zero detecting circuit 3 detects that contents of the counter 2 are 0 and adds an output l to a gate circuit 6 as 1. Further, a standard period PO is applied to a register 4 so that the count value of the changing point to be set is decremented by 1 independently of the presence of the changing point and the period is applied to a mode switching signal S to the counter 2 via the down- counter 5. Moreover, the clock of period T set to the register 4 is applied from the counter 5 to the circuit 6, the hysteresis characteristic is given to the period of subtraction of the detected number of changing points by the circuit 6 to prevent frequent line density switching around the reference value of discrimination of line density. |
