An approach was developed to estimate the values of diagnosability of digital systems with the novel structure of the minimal quasicomplete 7 x 7 graph. The proposed estimates of the values of diagnosability of the digital systems under consideration were established as the result of diagnosis of fault situations in a system of 7 users and 7 switches. Consideration was given to two variants of organization of the components of the analyzed digital system for which different estimates of diagnosability were established.