| 摘要 |
1. A method of generating a field deflection control signal in a picture display device, in which field pulses are obtained by means of counting half-lines in a counter (15), a counting pulse being generated as from the occurence of a predetermined count of half-lines, in which it is checked whether there is coincidence between the presence of a predetermined counting figure in the counter and the arrival of a separated field pulse which is derived from a signal received by the picture display device, in which, depending on whether there is coincidence or no coincidence during a certain number of fields, it is determined for resetting the counter to zero, whether the device is in a synchronised state for which coincidence has been detected a certain number of times consecutively, or in a non-synchronised state in the opposite case, and in which a memory (16) is used to store the number of half-lines counted by the counter, the field deflection control signal being obtained from the reset-to-zero signal of the counter, characterized in that when the non-synchronised state has been detected, at each arrival of a separated pulse the counting figure present at the instant at the output of the counter is stored in the memory, the counter being thereafter reset to zero after a certain delay, whilst when the synchronised state has been detected this counter is reset to zero at the instant at which its counting figure becomes equal to the figure stored in the memory. |
