A signal detection scheme for magnetic disc drives based on maximum likelihood sequence detection is proposed which refers to a channel with RLL 1, 7 coding and features a trellis with three states and five transitions. Owing to the RLL 1, 7 code, clock recovery is more stable than in partial response coded systems. The decoding gain amounts to 5 dB, and may lead to an increase in capacity by a factor of 1.8 when used for reading narrower tracks.