<p>The paper discusses reliability of a multi-level information-measuring system (IMC), which ensures monitoring of technical condition of technological facilities and traction power supply devices and their diagnostics, which is essential for quality of control of its modes. The technical condition of the IMC is assessed using probability vectors of its condition by applying a <br /> linear graph that allows defining the time of failure and other reliability measures individually for each level and the IMC as a whole. Analytically and graphically, it is shown that the failure time of the IMC is highly dependent on the failure rate of its lower stages. In the study of the efficiency of IMC and its structural components, classical theory of reliability assessment using a correction algorithm has been applied, which makes it possible to improve probability of the information-measurement system operation without fail.</p>