Scope Triggering Aid for Video Signals

This small circuit is useful for investigation and testing video signals. It allows you to select different triggering points on a VGA synchronisation signal by simply adjusting the trigger level of the oscilloscope. The trigger points are as follows (from the highest to the lowest trigger level):- Triggering on the back edge of the vertical sync signal.- Triggering on the back edge of the horizontal sync signal.- Triggering on the front edge of the horizontal sync signal.- Triggering on the front edge of the vertical signal.