This capacitor should be a Y capacitor, which is mainly used to eliminate common mode interference. It is also the capacitance that is respectively bridged between the two power lines and the ground (l-e, N-E), which usually appears in pairs. Based on the limitation of leakage current, the value of Y capacitance should not be too large. Here, the function of Y capacitance is 1. From a certain point of view, reduce the voltage of working ground and casing. It is equivalent to a large resistance grounding case. 2。 Reduce the common mode interference to its own circuit. 3。 Reduce external radiation and conduction. 4。 The capacitor shall be safety regulated capacitor (safety regulated capacitor refers to the one used in such occasions, that is, after the capacitor fails, it will not cause electric shock and endanger personal safety). It is necessary for the network access equipment.