STEL – electrochemical devices for producing electrochemically activated solutions – anolyte and catholyte from initial solution represented by fresh or low-mineralized water containing less than 5.0 g/l chlorides. STEL devices are fitted with a flow-through electrochemical diaphragm reactor represented either by one FEM flow-through electrochemical modular cell, or a combination of such cells (RPE reactor), a hydraulic system for feeding initial solution into the reactor and discharging electrochemical synthesis products from the reactor, as well as a power supply. Besides, depending on the model and manufacturing modification, STEL devices can be supplied with appliances for preparing concentrated sodium chloride solution for subsequent mixing with fresh water and obtaining initial solution, systems of automatic control of electrochemically activated solution parameters and the device operation parameters, automated system for periodic rinsing of the device with acid solution, a system to control storage capacity filling and a number of other gadgets and appliances characterizing the degree of STEL device engineering sophistication. STEL devices are mostly used for producing ecologically safe washing, disinfectant and sterilizing solutions for health care facilities, food industry, agricultural facilities and utility services.