Abstract: An efficient method and apparatus for determining, recording, and analyzing the phase history of a Line-in signal. The Line-in signal is coupled to a conventional demodulator. I and Q components are output by the conventional demodulator and coupled to an IQ quantizer. The IQ quantizer determines a quadrant on an I/Q plot from the amplitude of each component. A histogram is generated which indicates in which quadrant the Line-in signal was for a first sample, and in which quadrant the Line-in signal was for a second sample, the second sample having been taken immediately after the first sample. From this histogram, the number of times the Line-in signal transitions from one quadrant to another over a predetermined period of time is known.