Dommage l'article est pas traduit en francais :

http://en.wikipedia.org/wiki/High_impedance

In electronics, high impedance (also known as hi-Z, tri-stated, or floating) is the state of an output terminal which is not currently driven by the circuit. In digital circuits, it means that the signal is neither driven to a logical high nor to a logical low level - hence "tri-stated". Such a signal can be seen as an open circuit (or "floating" wire) because connecting it to a (low impedance) circuit will not affect that circuit; it will instead itself be pulled to the same voltage as the actively driven output. The combined input/output pins found on many ICs are actually tri-state capable outputs which have been internally connected to inputs. This is the basis for bus-systems in computers, among many other uses.

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