A key where the “hole cutting” or key video is different from the “key filling” or insert video. This is most commonly used with character generators that provide these two outputs, and allows the character generator to create a key border that is wider and cleaner than internally bordered keys. Such signals may also come from a colour camera that provides its own keying output or even a monochrome camera looking at an art card. An isolated key is always a luminance key, although composite chroma keys may be done with an isolated key source, ignoring the isolated input. AVC series switchers can defeat isolated inputs to standard type keys by turning key borders on. Also referred to as a Processed External Key.