In one aspect, the present invention comprises a method for tuning a power line communication inductive signal coupling device comprising a coupler and a plurality of capacitors, the method comprising: passing a carrier frequency signal through the coupler; sensing an amplitude of the signal; and switching the capacitors until the amplitude of the signal reaches a maximum. Accordingly, a data communications device receives data from a data provider, the data containing label information. A cathode layer on a dielectric oxide film of the anode body is connected to a cathode terminal and is coated with exterior coating resin with a part of the anode terminal and a part of the cathode terminal exposed.