Problems of overload and spark protection systems for high power RF generators, lasers, and radar; high-voltage interface RG-series relays; high-voltage switching devices; low-voltage switching devices for high-voltage power supply; applications for power engineering; applications for powerful radio-electronic equipment; high-voltage devices for industrial applications. Appendices: selected publications by the author; some types of RG-relays with special characteristics; environmental tests of RG-relays for MIL-STD-202 requirements; components recommended for use in HV protection devices; insulation materials for production of RG-relays; engineering equations for calculations of magnetic conductivity in magnetic circuits and electrical fields for some forms of electrodes.