Editing SCART (section)

=== 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 aspect ratio|16:9]]) signal
*9.5 V–12 V (nominal 12 V) means a normal ([[Fullscreen (aspect ratio)|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&nbsp;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. The same for the rare component YPbPr, which is in many cases implemented over a composite or RGB SCART.