The physical interface is a non-isolated 3-wire interface. Wires are SDA, SCL and ground. SDA and SCL lines are buffered. Ground is shared with power supply. There are small pull-up resistors for SCL and SDA. Connector is 8 pin male M12. Maximum cable length should not exceed 5 m and maximum capacitance between communication lines and ground should not exceed 500 pF.
