NRZ signaling uses just two signaling levels, where, e.g., a low voltage means logic 0 and a high voltage means logic 1, as shown in FIG. 1B. 4-PAM signaling on the other hand is a method used to transmit two bits per symbol using 4 signaling levels, as shown in FIG. 1A. In FIGS. 1A and 1B, Vsw signifies the maximum voltage swing between the various logic levels on the transmission line.