Description:
<jats:title>Abstract</jats:title><jats:p>This paper describes the design philosophy of a line driver and an automatic line equalizer applied for a 200 kbit/s ping‐pong transmission system using existing metallic pair cables. The semiimpedance matched line driver is appropriate from the viewpoints of transmitted pulse distortion and power consumption. The automatic line equalizer is composed of a frequency domain equalizer as well as a time domain equalizer. The frequency domain equalizer is used to compensate for wide line‐loss variations, while the time domain equalizer is used to compensate for intersymbol interferences due to cable gage changes and bridged taps. The decision feedback equalizer is used as the time domain equalizer. Gain vs. frequency characteristics of the frequency domain equalizer and number of required taps of the decision feedback equalizer are determined to minimize intersymbol interferences due to deviations between automatic line equalizer characteristics and various line characteristics. As a result of the design, the 200 kbit/s ping‐pong transmission system is operative for 99 percent of NTT's existing subscriber cables with 100 percent cable fill.</jats:p>