Many watermarking detection algorithms are correlation based, whereby an input signal is correlated with reference signals. The rear substrate includes at least two rear substrate parts connected to each other. This remarking serves as a performance indication for the packet gateway session admission control mechanism. A method for producing middle electrodes for a spark plug of an internal combustion engine is also proposed, in which an electrode base body has a precious metal platelet attached to it, the end face of the electrode base body oriented toward the combustion chamber being attached to the end face of the precious metal platelet oriented away from the combustion chamber. The rim andor one or more of the spokes have a leading andor trailing edge, at least part of which has an undulating configuration. Alternatively, a spiral resembling a spring may be used.