| 摘要 |
PURPOSE:To prevent an operation influenced by the abnormality of a synchronizing signal by detecting the abnormality with obtaining a discriminating signal at a field discriminating circuit from a horizontal and a vertical synchronizing signals separated at a synchronizing signal separating circuit. CONSTITUTION:An inputted synchronizing signal Sync is supplied to an HD separating circuit 1 and a VD separating circuit 2 and is separated, and an HD signal and a VD signal are separately outputted. Furthermore, these signals are supplied to a field discriminating circuit 3 and a field discriminating signal FD is obtained. The FD signal is inputted to a leading edge detecting circuit 4 and a trailing edge detecting circuit 5. These detecting circuits consist of a circuit which forms a regulated pulse width like a monomultivibrator, etc. and the pulse width is set as longer than 1V period and as shorter than 2V period. The output of each detecting circuit is inputted to an AND gate 6 and with latching the output by a latching circuit 7, a synchronization abnormal signal is outputted. For example, it is possible to prevent the print output that a picture quality is excessively deteriorated with inhibiting the output of a print by the synchronization abnormal signal. |
