During the lifetime of railway automation and telematics systems (RTAS), it is necessary to guarantee high level of safety, which numerically is defined as fail-safe or continuous working time (Uptime). RTAS safety level is based on maintenance technology and strategy. In RTAS for relay part TBM (Time Based Maintenance) with new or renovated, but degraded, elements independently of elements’ condition (PM-Preventive Maintenance) is adopted. Results achieved in the work can affect the quality and technology of maintenance, level of safety and reliability of system’s, trend in development of subsystem of monitoring and diagnostics, diagnostics tool’s in computer based interlocking (CBI) system’s. In the work, as practical result, is given: pulse relay’s anchor’s and contact systems’ state diagnostic method; electronic code transmitter with self-diagnostic function (LR patent LV14466); battery condition’s diagnosis after the internal resistance method for increased precision; load generator’s use in battery’s diagnostic tasks (LR patent LV14473).