The invention relates to an apparatus for igniting a fuel mixture. Set apparatus comprises an ignition system for generating a high-voltage ignition voltage as well as a circuit device comprising a circuit for superimposing a high-frequency signal on to the high-voltage ignition voltage. The apparatus further comprises a spark plug in an engine block as well as a transmission element for transmitting the ignition voltage, onto which the high-frequency signal has been superimposed, to the spark plug. The transmission element includes a contact element which is provided with an electrically conductive coating along at least one portion of the longitudinal axis of the contact element, the impedance of the coding being lower than the impedance of the contact element.