A bio-signal measurement apparatus comprises tool-less connectors, coupling targets, a controllable coupling selection arrangement, and a control arrangement. The tool-less connectors are for an electric contact with a separate docking apparatus or an electrode arrangement. The coupling targets include a battery and a data communication unit that performs electrically a plug-and-play data transfer with the separate docking apparatus. The tool-less connectors, the number of which is three, are electrically coupled with the controllable coupling selection arrangement, which electrically couples all the tool-less connectors with only one of the coupling targets at a time in response to control from the control arrangement. The battery receives electricity from the tool-less connectors for charging the battery through the electric coupling caused by the coupling selection arrangement under control of the control arrangement during a first time window when the bio-signal measurement apparatus is connected with the docking apparatus. The data communication unit sends and/or receives data through the tool-less connectors using the plug-and-play data transfer based on the electric coupling caused by the coupling selection arrangement under control of the control arrangement during a second time window when the bio-signal measurement apparatus is connected with the docking apparatus.