Because residential power outlets have three wires—hot line (H), neutral (N) and ground (G)—the ISOBAR4ULTRA protects all three, covering the two protection modes: full normal mode (H-N) and common mode (N-G/H-G). our devices plug into four widely spaced NEMA 5-15R outlets, which are arranged in two exclusive isolated filter banks. These internal barriers filter out electromagnetic interference (EMI) and radio frequency interference (RFI) that can disrupt your electronics and inflict hardware damage or data loss.