Electronics Engineering Question:

In digital ciruit, the gate output can be only high or low. In highstate the output source current at a minimum voltage, greater than ~2.8V if load(fan out ) is proper. In low state it will sink current at max output voltage less than ~0.8V. Some times it is derirable to have a state output both not high or low. with neither sinking or sourcing (with high output impedance). This is called tristate. Tristate output cannot change output condition of succeding logic gates, unless tristate is disabled.