A personal wearable EEG monitor with a battery, said EEG monitor comprises - a base part having signal processing means, - an electrode part with at least two electrodes (11, 12) for measuring an EEG signal of a person, said electrode part comprises means for converting the EEG signal into a digital signal, and - a databus comprising two electrical wires for transferring data between said base part and said electrode part and for providing power either from the base part to the electrode part or from the electrode part to the base part through said two electrical wires, wherein said base part is prepared to be arranged behind the ear of said person and the electrode part is prepared to be arranged in the ear canal of said person, wherein the databus is configured to apply at least three different states in different time slots, where a first state is for transfer of power from the battery to the electrode part, a second state is for transmission of signal from said base part to said electrode part, and a third state is for transmission of signal from said electrode part to said base part, wherein said battery is arranged in the base part and a capacitor is arranged in the electrode part, wherein said capacitor is configured to be charged during said first state for transfer of power, and is configured to supply power in the second and third state where no power is transmitted from the battery through the databus, the monitor being characterized in that said electrode part comprises a receiver or speaker for providing a sound signal to said person, wherein said receiver or speaker is configured to be short-circuited during the second and third state during transmission of signal through the databus, wherein short-circuiting the receiver is achieved by controlling four switches of an H-bridge included in the electrode part. - a base part having signal processing means, - an electrode part with at least two electrodes (11, 12) for measuring an EEG signal of a person, said electrode part comprises means for converting the EEG signal into a digital signal, and - a databus comprising two electrical wires for transferring data between said base part and said electrode part and for providing power either from the base part to the electrode part or from the electrode part to the base part through said two electrical wires, wherein said base part is prepared to be arranged behind the ear of said person and the electrode part is prepared to be arranged in the ear canal of said person, wherein the databus is configured to apply at least three different states in different time slots, where a first state is for transfer of power from the battery to the electrode part, a second state is for transmission of signal from said base part to said electrode part, and a third state is for transmission of signal from said electrode part to said base part, wherein said battery is arranged in the base part and a capacitor is arranged in the electrode part, wherein said capacitor is configured to be charged during said first state for transfer of power, and is configured to supply power in the second and third state where no power is transmitted from the battery through the databus, the monitor being characterized in that said electrode part comprises a receiver or speaker for providing a sound signal to said person, wherein said receiver or speaker is configured to be short-circuited during the second and third state during transmission of signal through the databus, wherein short-circuiting the receiver is achieved by controlling four switches of an H-bridge included in the electrode part.