For detuning of radio-frequency coils (in magnetic resonance imaging and spectroscopy, for example), a conducting element (102) of a transmission cable is configured to form a primary resonant circuit tunable to at least one first resonance frequency. A second conducting element (104) of the transmission cable is configured to form a switching circuit that is electrically insulated from and reactively coupled via inductive coupling and/or capacitive coupling to the primary resonant circuit, and is adapted to tune the primary resonant circuit to at least one second resonance frequency, thereby detuning the primary resonant circuit.