Surge arrester 4P T2 TNS/TT backup fuse up to 315A In 20kA Imax 40kA. Surge arrester type 2 in 3+1 circuit, for protecting three-phase TT and TN-S systems with optical fault signal. Connections for the active conductors from below and for earth/PE from above. Biconnect terminals for connecting round conductors and wiring bridges. Modular device according to DIN 43880.