To achieve a safe transition from the ignition of a plasma in incision mode to the combustion of the plasma during a cutting mode, an electromedical device to supply an instrument with electrical power is equipped with an ignition recognition mechanism formed by a sensor device. This ignition recognition mechanism switches the HF generator provided in the device from an incision operating mode to a cutting operating mode as soon as ignition is recognized. The switching is brought about by the switching of an HF modulation from a low crest factor in the incision operating mode to a high crest factor in the cutting operating mode.
