ALLNET Powerline phase coupler/signal bridge for DIN hat rails assembly, 3phase version + extra galvanically isolated phase for bridging FI_Schutzschaltern, home coupling or cross-current meter coupling, frequency range 1-70 MHz, temperature range: -25°C** IMPORTANT: 3 phases + "L/N" . Better coupling increases range compared to standard phase coupler. Multiple circuits can be connected to this ALL16881PC adapter. FI's can be bridged with multiple ALL16881PC **Attention. This item may only be installed by authorized repair shops.