Surge protective devices SPD type 1- type 2 protect low-voltage consumer systems against lightning currents and surge voltages as they are tested as SPD type 1 and type 2 according to IEC 61643-11. The devices are compatible with the System pro M compact series. The SPD with "TS" are optionally equipped with a auxiliary contact. The variants with "reserve varistor" (s) offer additional protection for the system, as the SPD is not completely disconnected from the mains at the end of its service life, but with an additional smaller varistor still guarantees basic protection and the system thus until the surge arrester is replaced is still protected