These small filters are popular devices that can be supplied with a wide range of X and Y values to suit most purposes.

In a Delta Suppressor, capacitors are connected between the Live, Neutral and Earth terminals. As the frequency of the R.F.I. rise, the impedance of these capacitors falls thus attenuating the R.F.I. at the mains terminals.

These filters are constructed using Class X and Y capacitors with a resistor to discharge the device.