Technical notes and performance Our filters are specifically designed to combat both "Asymmetrical" as well as "Symmetrical" interference, both being effectively suppressed by the introduction of High Frequency Capacitors and a single Choke. In addition we have also incorporated an Earth Line Choke to stop interference through the mains earth line, finally we use a screened Mains Cable to eliminate the effects of radiated noise interference. Operating Voltage 220-250V ac Max Current rating 13A Max Surge Protection L-N 6500A, L-E 4500A, N-E 4500A Neon Indication None- these can inject noise into the system Mains Cable Shielded with Aluminium foil IMPORTANT Insertion loss measurements below were carried out asymmetrically. Some manufacturers only test symmetrically which appear to offer better results Single stage Filter Insertion Loss dB 150kHz.62 3 MHz.35 30 MHz.30 1 GHz.15