Secure System transmission data.

The invention relates to a data transmission channel for a function of an onboard aircraft equipment comprising a first chain of calculation and a second calculation chain executing the same function as the first channel to enable the calculation of the first chain, characterized in that the second calculation chain using the same hardware resources as the first chain and comprises, connected in series, transforming means (3) of the input data, an acquisition means (4), the computer ( 5), means of processing the compensation (51) and the comparing means (53) so that the second calculation chain executes a dissimilar calculation of the first calculation chain and the processing of compensating means (51) compares the data results of the first and second string calcul.L'invention is particularly suited to the aeronautical field.