Do you even know what a common mode choke is? At first let me explain what a choke really is. The choke is a device which is inserted in wires and cables to restrict noise frequency. This is basically considered a discrete device aimed to reduce the radio frequency current flowing across the cables. The common mode choke is very much an electrical thing and very interesting too. Take for example a cable; the cable may constitute of two conductors or more.
The common mode choke may of use in case of an N-conductor cable having around N-insulated conductors. The common mode choke is basically transparent at every mode other than the common mode. Strangely the common mode choke offers low or no resistance for differential current. However, the situation is quiet different for a common mode. It looks more of an open circuit then. So now you know how the common mode choke works?