Adaptive and automatic quantised feedback equalisers of telephone lines for data transmission are studied. In particular, equalisers which use a steepest-descent algorithm with a minimum mean square error criterion are considered, and the effect of 2-level quantisation on the mean square error in the steady state and on the conditions of stability are analysed. The effect of the ‘random walk’ of the tap coefficients on the mean square error in the steady state is also investigated. Finally, a comparison of the performance of six equalisation schemes is made using computer simulation. These schemes include nonrecursive and hybrid networks, with and without signal quantisation.