A hearing aid comprises a power supply, a microphone and a base part to be arranged outside the ear canal of a hearing aid user, and an ear plug part to be arranged in the ear canal of a hearing aid user. The ear plug part comprises a receiver for transmitting sound into the ear canal, and a transducer generating a signal to be transferred to said base part. A databus connects the ear plug part with the base part. The databus comprises two electrical wires adapted for transmission of signal to the receiver, and for transmission of signal from the transducer to the base part. The databus provides power supply either from the base part to the ear plug part, or, from the ear plug part to the base part. The invention further provides a method for communicating between two parts of a hearing aid.信号処理手段(23)を有するベース部(1)と人のEEG信号を計測する少なくとも2つの電極(11,12)を有する電極部(2)を備える個々人に装着可能なEEGモニタである。上記電極部(2)は上記EEG信号をデジタル信号に変換する手段を備える。上記EEGモニタは上記ベース部(1)と上記電極部(2)の間でデータを転送し,かつ一方の部から他方の部に電力を提供するデータバスを備えている。上記データバスは2本の電気ワイヤの適用に適するものである。
