History Lesson.
My experience of this "ice detector" was that it was a waste of weight and complexity. It usually illuminated the warning long after the 'frame had accreted ice or alternatively gave frequent false warnings. Why BAE abandoned the "hot rod" ice detector as used on the 111 and the 125 is a mystery. It was a delightfully simple and foolproof device, the only quirk was the tendency to "hum" at certain AOAs!