Commonly used low-pass filter circuit b

Commonly used low-pass filter circuits
Commonly used low-pass filter circuits are shown in the figure.
Figures (a) to (c) can suppress high-frequency interference;
the varistor in Figure (b) can absorb lightning surge voltage;
Figure (d) can inhibit low-frequency interference;
Figure (f) is used for power supply decoupling . You can choose to use it according to the specific situation.