In the 1930s, Walther Bender obtained patents for several insulation monitoring devices for ungrounded systems in mining applications. The decision was made to cover grounded systems, as well. Residual current monitoring devices and ground fault circuit interrupters were developed and added to the product line. Bender devices began to appear in industrial applications throughout the world and protection relays were developed. Its devices help prevent accidents and protect people and equipment by supporting electrically safe environments. Bender products include protection relays for single and three phase systems, ground fault monitoring devices for grounded systems, ground fault circuit interrupters for portable and fixed installed use, insulation monitoring devices for ungrounded systems, power supplies for hospitals that include line insulation monitors and medical testers.