A choke coil is an inductor designed to have a very big reactance at a determined frequency or frequency range. It is either used to avoid the passage of alternating current from one part of the circuit to another while the passage of direct current is allowed or to avoid the passage of common mode current while the passage of differential mode current is allowed.
Choke coils are used in electronic appliances. They are very useful in televisions as well as in many other devices by acting like filters. Common mode choke coils are useful in a broad range of precaution of electromagnetic interference (EMI) and radio frequency interference (RFI) of feed lines and for precaution of malfunctioning of several electronic appliances. Additionally, common mode choke coils are also used in circuits like CC-CC converters and load circuits to reduce the noise resulted from the leaks of each part of feed lines.