An apparatus for ascertaining and/or monitoring at least one fill-level of at least one medium in a container according to a travel-time measuring method and/or a capacitive measuring method by means of at least one measuring probe. A capacitive measurement circuit, which produces a low frequency measurement signal on the measuring probe, a time-domain reflectometer measurement circuit, which produces a high frequency, electromagnetic signal sent out as a sent signal and a control/evaluation unit, which controls both measurement circuits are included. Also included is a diplexer, which sends the low-frequency measurement signal and the high-frequency, electromagnetic measurement signal to the measuring probe and effects a signal separation of the high-frequency, electromagnetic measurement signal into the first signal path of the time-domain reflectometer measurement circuit and the low-frequency measurement signal into the second signal path of the capacitive measurement circuit.