The present invention relates to a device (700a, 700b, 700c) for wireless transmission of data and/or power between the device and another device of a system, in particular of a patient monitoring system. To meet stringent relative time errors at low complexity the device comprises a connector (701) comprising a data transmission unit (703) and a magnetic coupling unit (702, 704) for transmitting power to and/or receiving power. A detection unit (705) detects coupling of a counterpart connector of another device of the system with the connector (701). A control unit (707) uses the detection that a counterpart connector of another device of the system has been coupled with the connector (701) as a trigger to determine and/or reset a relative time difference between a clock signal used by the device and a clock signal of the other device using i) the high frequency power signal of the magnetic coupling unit (702, 704) and of a magnetic coupling unit of the counterpart connector and/or ii) a received time calibration signal for determining and/or resetting the relative time difference.