the difference in phase-shift between the two directions of propagation in a non-reciprocal phase-shifter NOTE - The use of this term for other types of phase difference such as between states in a digital phase-shifter is deprecated.the difference in phase-shifts provided in the two opposite directions of propagation by a non-reciprocal phase-shifter NOTE - The use of this term for other types of phase difference such as between states in a digital phase-shifter is deprecated.