A process for preparing support signals (g'i) to support a demodulator (Dm) by a data decoder (Dd) in the coded transmission of data bits (dk) by means of an M-stage channel symbol alphabet. To shorten running times of the support signals (g'i) fed back from the data decoder (Dd) to the demodulator (Dm), said signals have a limited information content which, for example, can run out in a datum to which the transmitted channel symbols (c'i) of several groups of such symbols estimatedly belong or in which group of statuses the path through the treillis diagram is estimatedly to be found.
