A logic device that has three possible output states: ‘1’, ‘0’, and ‘high impedance’ (rather than the normal two states ‘1’ and ‘0’). The high-impedance state isolates the device electrically from the rest of a circuit. Tristate logic gates allow many devices to be connected onto the same data lines, such as data and address buses. However, only one device is ‘connected’ at any one time, all others being in their high-impedance state and thus electrically disconnected.