Yes, that is a normal abbreviaition; it means "tout ou rien", in other words "all or nothing" — but in practice, in EN equivalent terms, we'd talk about a "digital" input etc. — one that can only have 2 possible states, like on/off, 0/1, low/high, etc. (as distinct from a continuously-variable analogue input)

So your abbreviation 'DIG' for digital is perfectly consistent

Normally, the word order would suggest it would be "accessory digital", but I can't quite see how that would work, and you don't give enough context for us to be really sure how it is being used here.

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Note added at 23 mins (2007-02-28 20:39:01 GMT)
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In other contexts, it is also sometimes called "binary", but that's a bit confusing, since it can also imply all sorts of other things.