Phoenix Contact 2905338 A plug-in surge arrester designed according to Type 2/Class II standards is suitable for 2-phase power supply systems that have separate live (L) and neutral (N) conductors as well as a protective earth conductor (PE) in a four-conductor setup, which includes L1, L2, N, and PE. This type of system often features remote indication contacts that provide an indication of the arrester's operational status or any potential issues.