EFEN GmbH was founded in 1922 by Otto Frees in Neudorf, which today is known as Martinsthal. The original activities concentrate on the assembly of electrical fuses for the automotive industry. Very soon, the product portfolio was expanded by the production of fuses for all kinds of applications including current-limiting fuses for low- and-medium-voltage power distribution systems. At the start of 2006, the EFEN Group was bought by the Swiss Weber AG, a company belonging to the Hager Group.