To allow bidirectional data communication to be realized in hearing aids which have only a restricted installation space, the earphone, i.e. the electroacoustic transducer unit, is used as the transmitter and the telephone coil as the receiver for high-frequency signal components. This makes it possible to dispense with the installation of an additional antenna, generally of a large volume, that is optimized for transmitting and receiving operations. If appropriate, a small additional antenna may also be used purely as a receiving antenna for high-frequency signals.