The paper presents an example of mathematical modeling of the process of reproducing units of physical quantities by installations of the highest accuracy and their transfer to measuring instruments in the form of a non-stationary service system. The use of non-stationary service systems makes it possible to evaluate the efficiency of the process under overload conditions at the directive interval, as well as to evaluate the most important characteristics of the functioning process, for example, such as the probability of failure to perform reproduction and transmission of units of values by installations of the highest accuracy in a timely manner, etc.