The structure of self-checking digital devices with calculation control by two diagnostic parameters has been proposed. The belonging of being formed in in-built control circuit codeword to constant-weight code “2-out-of-4” is used as a first parameter. A second parameter is the belonging of each being calculated function to the class of self-dual Boolean functions. The specificity of being described in the article the organization structure of self-checking digital devices is the presence of the circuit of preliminary compression of signals from diagnosis object. Its usage allows to cut structural redundancy of end device down essentially. Besides, nevertheless, errors can be masked at the inputs of compression elements. The article underlines the features of the choice of being compressed outputs of diagnosis object and the algorithm is proposed allowing to minimize the risk of undetectable error occurrence at compression scheme output. The algorithm of built-in control scheme synthesis by two diagnosis parameters has been presented which takes into account conditions for the formation of full set of test combinations for testers and elements of transformation in signal correction block. The example of realization of synthesis algorithm for fully self-checking device Logisim is considered. Key features of built-in control scheme are denoted; the scheme is embodied according to the proposed structure. The way of organizing calculation control by two diagnostic parameters is of interest at the synthesis of fully self-checking digital calculation devices and systems.