The simplest filter for this purpose is the one shown in the figure consisting of two coils and two capacitors in parallel. The coils can be wound on ferrite rods or even ferrite rings consisting of 40 to 60 turns of wire with thickness according to the power of the powered device. For televisions and other medium consumption devices (up to 200 W), wire 22 can be used. The capacitors used are 100 nF and must have insulation voltages of at least 400 V if the network is 110 V and 600 V if the 220 V network. An interesting feature of this filter is that it also offers some protection for certain types of transients that propagate through the network and can affect the most sensitive powered circuits.
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