A choke is an inductor designed to have a high reactance to a particular
frequency when used in a signal-carrying circuit. Choke coils are inductances
that isolate AC frequency currents from certain areas of a radio circuit. Chokes
depend upon the property of self-inductance for their operation. They are used
to block alternating current while passing direct current. Common-mode choke
coils are useful in a wide range of prevention of electromagnetic interference (EMI)
and radio frequency interference (RFI) from power supply lines and for
prevention of malfunctioning of electronic equipment.