| 摘要 |
PURPOSE:To produce a vertical synchronizing pulse which excels in the noise resistance by discriminating a synchronous or an asynchronous state and then giving inversion or non-inversion to a T type FF based on the result of said discrimination. CONSTITUTION:It is supposed that the signals given from a frequency separating circuit 15 are vertically synchronous in case both inputs of an OR gate 22 are set at L levels. Thus these signals are regarded as synchronizing signals. Then the trigger is applied to a T type FF through the gate 22. As a result, an FF23 is inverted with its output Q changed to an H level from an L level. Otherwise it is considered that the signal is a noise and the output of the gate 22 kept at an H level. Thus the FF23 is not triggered with no change produced to the Q output state. In such a way, a vertical synchronizing pulse which excels in the noise resistance can be obtained through an output terminal 14. |
