RFI power line filters can be thought of as "impedance mismatching networks" at higher frequencies in the attenuation band. Network analysis shows that the greater the mismatch of filter impedance to terminating impedance, the more effective the filter is in attenuating RF energies. Common mode power line impedance is considered to be low (on the order of 50 ohms). Thus, following the concept of impedance mismatch, CORCOM power line filters employ a high common mode impedance (series inductance) on the power line side of the filter. For load (equipment) side common mode impedance mismatch, CORCOM products are available with a high impedance (series inductance) or a low impedance (shunt capacitance). High (common mode) impedance filters for use with low impedance equipment include the EP, H, 6amp Q, R, and V Series. Low (common mode) impedance filters for use with high impedance equipment include the B, EC, ED, EF, G, K, N, 3amp Q, S, SK, T, W, X, Y, and Z Series. Knowing the input impedance of your equipment, then, may be useful in initially selecting the filter series most likely to solve your RFI problems. However, since this impedance is almost certainly complex (having both resistive and reactive components), it may vary widely over the RFI frequency range. Hence a variety of series should be evaluated in your quest for the most effective filter in any one application.