"Dave Plowman" wrote in message ...

[Detecting whether the TV is using an RGB feed]

The easy way to check is by slowly removing/connecting one of the
SCART cables at an angle - you can usually make one of the RGB feeds
break up first.

There's an easier way than that: if the TV is using RGB then its colour
(saturation) control will have no effect. If the picture goes to black and
white when you turn the colour right down, the interface must be either
composite or Y/C, not RGB.

--
Andy