A comparator detects rising transitions of an input waveform and another comparator detects falling transitions. Each comparator detects their respective transition with a different threshold voltage. The outputs of these comparators are multiplexed into the clock input of a flip-flop. The flip-flop's inverted output is connected through a time delay to the input of the flip-flop to form a toggling configuration. The output of the time delay is also connected to the select input of a multiplexer that controls the multiplexer to multiplex the outputs of the two comparators into the clock input of the flip-flop. The threshold voltages chosen for the two comparators are chosen to be in the center of the incident edges of the distorted signal of a source-terminated transmission line. The time delay is chosen to be longer than the difference between the arrival of the incident wave and the arrival of the first reflected wave.