The effectiveness of noise attenuation depends heavily on the source and load impedance. EMI Filters function as a mismatching network between the source and load impedance at higher frequencies. The greater the mismatch, the more effective the Qualtek EMI Filter will be at attenuating the interference. In most cases, the power line presents low impedance. The Filter line side should then present high impedance. Equipment, on the other hand, can be either high or low impedance. High impedance equipment such as linear power supplies should use a filter with a low impedance or a shunt capacitor at the load side to create a mismatch. Low impedance equipment such as switching power supplies, synchronous motors, or shunt regulators should use a Qualtek Electronics EMI Filter with high impedance at the load side and should have a series inductor.