1. A collision recovery signal processing unit for use with a multiple-access telecommunications channel comprising antenna means 50 having a plurality of branches; a plurality M of spatio-temporal filter means 52, 54 each arranged to estimate a signal received by the antenna means by application of a different sequence of training-like symbols TLS and to supply a corresponding candidate signal, SC 1 to SCM; and signal selector means 56 arranged to select from the candidate signals one or more signals in accordance with a predetermined criterion.