An equalization circuit that allows particularly for lowpass filtering by transmission lines comprises a compensating equalizer controlled according to whether the edges between bits in the data waveform are early or late. Adjusting the equalization causes edges to appear in the same place, whereas if the adjustment is incorrect certain edges will be late and certain edges will be early depending on the history of “1”s and “0”s in the data stream. This is an effect of so-called intersymbol interference. The control mechanism includes circuits for recognizing patterns of “1”s and “0”s in the recent history of the data waveform whose occurrence is used to trigger the adjustment of the equalizer.