Device for extracting an image synchronising signal from a television signal

摘要

The invention relates to a device for extracting an image synchronising signal from a television signal. This device comprises a known synchronising and scan control circuit 1 which provides line SyL and frame SyT synchronising pulses. These frame synchronising pulses are divested of interference which may follow them with the aid of a circuit including a monostable multivibrator 4, an AND gate 5 and an OR gate 6. These clean pulses SyTF are then transformed into short pulses SyTFR and merged with the line synchronising pulses SyL by an AND gate 8. Owing to the shift of half a line between the first and second frames of each image, only the synchronising pulses of the first frame are retained. The invention applies to the identifying of the lines of a television image. <IMAGE>