An active EMC filter for medical applications allows reducing the leakage current normally induced by large phase-to-ground capacitances. The system may use a segmented MAC architecture which may have a method of re-purposing MAC IP addresses for inside MACs and outside MACs, and leveraging what would normally be the physical signaling for the MAC to feed into the switch. Each of the first and second wiring currents has a first polarity when generating a \u201c1\u201d and a second polarity, different from the first polarity, when generating a \u201c0\u201d. The dust-proof cover is disposed pivotally on the base seat, and has an engaging portion disposed between the first and second pushing portions, and a cover plate portion connected to the engaging portion.