A method for detecting signals affected by intersymbol interference
provides for a path memory in the form of a trellis admitting survivor
paths comprising a first and a second stage. The first stage includes a
shift register exchange with a given number of states and a given length
.lamda.. The first stage outputs a first state S.sup.Ak.sub.k-.lamda. on
the survivor path for the best state A.sub.k, and a second state
S.sup.Bk.sub.k-.lamda. on the survivor path for another state B.sub.k.
The second stage is configured as a two-state shift register exchange
having a respective memory length .LAMBDA., including respective first
and second registers. In the respective first and second registers the
survivor paths are stored leading to a respective first
.sigma..sup.0.sub.k and second .sigma..sup.1.sub.k state, whereby the
respective first register contains the backend of the best survivor path,
while the respective second register contains the backend of an
alternative survivor path.