A high frequency transformer for a welding-type device is provided. The energy of the partially reflected trapped pulse is restored before beginning another round trip in the delay line. In one embodiment, the cover includes a cap and a hanging casing. An array of data dots, detectable by the reader, is printed in the data area to represent said data. This decreases the tolerance in the flow resistance of the injection nozzle upon a partial stroke of the nozzle needle, and thus makes a more-precise control of the injected fuel quantity possible.