The invention relates to an apparatus for insulation monitoring between a low-voltage supply system and a high-voltage supply system, wherein the apparatus can be connected both to a high-voltage positive connection and also to a high-voltage negative connection and also to the low-voltage supply system, wherein the apparatus has a plurality of electrical contacts for coupling monitoring connections to the high-voltage circuit by means of a respective high-voltage positive connection and by means of a respective high-voltage negative connection, it being possible for said contacts to be connected in different sections of the high-voltage supply system.