1. Device for estimating a series of symbols, the symbols being related to each other by a parity relationship previously created by an encoder, the estimation taking place through a function having several components performing a calculation of probabilities corresponding to a state of the encoder, these probabilities including: first probability values, resulting from the observation of the effects of the previous states of said encoder on the current state, second probability values, resulting from the observation of the effects of the subsequent states of the encoder on the current state, and third probability values, representing the belonging of a symbol to a predetermined part of an encoding alphabet, this device having: calculation means, specific multiplexing means, means for controlling said multiplexing means, and storage means, for storing estimations of said symbols, said multiplexing means being controlled by said control means and adapted to cooperate with said calculation means so that, not only said first and second probability values, but also said third probability values, are obtained by one and the same circuit from a plurality of predetermined parameters.