On the base of Sr90, the source of electrons with selectable energy has been constructed. The energy of emitting electrons is tunable by current loaded to electromagnet. The range of energy of electrons is from 200 keV up to 1.5 MeV (maximum energy is limited by energy of Sr90 source). The system which includes vacuum pump is controlled by PC software. System will be used for testing of detectors (mainly scintillating detectors, pixel detectors and strip detectors).