SCART - Blanking and Switching

Blanking and Switching

Two pins provide switching signals.

Pin 8, the switch signal pin, carries a DC voltage from the source that indicates the type of video present.

0 V–2 V means no signal, or internal bypass

4.5 V–7 V (nominal 6 V) means a widescreen (16:9) signal

9.5 V–12 V (nominal 12 V) means a normal (4:3) signal

Pin 16, the blanking signal pin, carries a signal from the source that indicates that the signal is either RGB or composite.

0 V–0.4 V means composite.

1 V–3 V (nominal 1 V) means RGB only.

The original specification defined pin 16 as a high frequency (up to 3 MHz) signal that blanked the composite video. The RGB inputs were always active and the signal 'punches holes' in the composite video. This could be used to overlay subtitles from an external Teletext decoder.

0 V–0.4 V means composite with a transparent RGB overlay.

1 V–3 V (nominal 1 V) RGB only.

There is no switching signal to indicate S-Video. Some TVs can auto-detect the presence of the S-Video signal but more commonly the S-Video input needs to be manually selected.