A circuit for a fill-level measuring device is for the fast switching-on of a high-frequency element on a ground port is disclosed. The circuit comprises a switching unit with a circuit mass; a high-frequency element with a high-frequency mass; and a coupling element that couples the two masses together and at the same time insulates them from each other in a direct-current manner. In this way the switching unit can be arranged on the GND port of the HF-element, without influencing the HF characteristics of said HF element.