Issues related to circuitry of electronic devices of industrial automation are comprehensively described. Schemes and system properties of basic elements - operational, current-difference and measuring amplifiers, comparators, active filters, logic elements and units, phase-locked loops, microprocessor devices, power supplies, switches and signal converters are considered. Much attention is paid to electromagnetic compatibility and noise immunity, methods of engineering calculation of nodes. For engineers and technicians in the field of industrial automation, electronics, measuring equipment.