Comparison of different types of digital transmission over metal conductor pairs not subject to channel crosstalk

Digital transmission over metal conductors was studied, using the ratio of the square of the eye opening to the noise power at the output of an ideal equalizer as quality measure. Quality was plotted as a function of the duration of the rectangular pulses, the roll-off factor (r), the cosine transfer function, and the attenuation of the metal conductor at the Nyquist frequency of the binary transmission. For r = 0.3 and a cable attenuation between 105 dB and 130 dB, quaternary transmission gives the best results,while modified triobinary and quinary give the worst.