This is a simple analog video mixer based on the LM1881 sync separator.
There is a cross fader, cross dissolve (50% in the center). And a fade effect, with 3 settings. The fade effect quickly charges a capacitor with the video signal, and slowly discharges it back into the video signal. Selecting the filter will filter out the color information, resulting in a black and white image.
Because all video devices have slightly different video sync speeds the selected video will stand still on the screen and the other video signal will scroll horizontally. That is where the name schele comes from, which is dutch for cross eyed.
It works by taking the sync of one of the two connected video signals, and pushing it under the output video signal. So blanking periods will partially be ignored, making it not 100% valid video signal.
Compatibility: NTSC and PAL