A device (10) for the detection of quadrature signals of a signal unit (11; 21) has a common power supply line (VBATT_A & B) and a common ground wire (GND), and emits at least two out-of-phase square wave signals (IA, IB; IS, ID) during operation for analyzing the same in an analysis unit (16), wherein both out-of-phase square wave signals (IA, IB; IS, ID) are applied to the common power supply line (VBATT_A & B) at different amplitudes, wherein the two out-of-phase square wave signals (IA, IB; IS, ID) are modulated onto the supply current (I0)), and wherein the analysis unit (16) is or can be connected to the power supply line.