An application device for applying a conductive insert on a tyre being processed. The application device includes a supply device for supplying a conductive liquid elastomeric compound, and an applicator having a movable surface for being operatively coupled with the supply device and receiving the conductive liquid elastomeric compound. The movable surface is for being placed in contact with a rotating tyre being processed and for applying the conductive liquid elastomeric compound on at least one coil of axially adjacent and/or partially superimposed coils. The applicator generates depressions in the tyre in a pattern defined by elements in relief and fills the depressions in the tyre with the conductive liquid elastomeric compound to covering the elements as the depressions in the tyre are generated.