A signal range from ground to a positive value (e.g., 0 to +5 V).
A signal range that is always positive or always negative, for example 0 to +10 V.
An analog signal range that is always positive (through zero.)
A signal being measured is said to be unipolar when the voltage on its 'high' terminal is always the same polarity (normally positive) in relation to its 'low' terminal.
A term used to define the clamping characteristics of SAD's. A unipolar SAD will suppress in one direction only, i.e. only positive or negative transients.