An audio appliance includes two external connections for connection to external loudspeakers, and includes means for establishing an electrical signal between the external terminals that is representative of an audio source in order to inject an excitation electric current into each external loudspeaker. Means are provided for incorporating a component at a “detection” frequency that is situated outside the audible spectrum in the electrical signal that is established between the external terminals, together with means for detecting an electric current flowing between the external terminals and having a frequency corresponding to the detection frequency. This is applicable in particular to systems comprising a mobile appliance and a fixed docking station incorporating a woofer and designed to receive the mobile appliance.