Circuit arrangement for operating light sources, having: - an input for inputting an input voltage, - an output for outputting an output current, - a first interface for controlling the circuit arrangement, - a second interface, wherein the circuit arrangement is configured to set two different operating modes: - in a first operating mode, the circuit arrangement is configured to be controlled by way of the first interface and to measure a current present across the second interface and to determine a current requirement for the output in accordance with the measured current, - in a second operating mode, the circuit arrangement is configured to be controlled by way of the first interface and to receive information about the output current that is to be set at the output, characterized in that the circuit arrangement is configured to use the second interface in the second operating mode to receive digitally encoded information from a sensor connected to the second interface, to process this information and to pass this processed digitally encoded sensor information on to the first interface, wherein the second interface has a voltage source (Q1, Q2, U2, R903, R904), which delivers a predetermined voltage, and wherein the voltage source (Q1, Q2, U2, R903, R904) is designed to supply power to the sensor in the second operating mode, and a measuring circuit (R902, R901, R153) for measuring a voltage applied across the second interface, wherein the second interface is configured, in the second operating mode, to digitally receive the digitally encoded information from the connected sensor by detecting a clocked voltage change between two different voltages at the output of the second interface, wherein a first higher voltage and a second lower voltage of the second interface represent digital states of the digitally encoded information. - an input for inputting an input voltage, - an output for outputting an output current, - a first interface for controlling the circuit arrangement, - a second interface, - in a first operating mode, the circuit arrangement is configured to be controlled by way of the first interface and to measure a current present across the second interface and to determine a current requirement for the output in accordance with the measured current, - in a second operating mode, the circuit arrangement is configured to be controlled by way of the first interface and to receive information about the output current that is to be set at the output, the circuit arrangement is configured to use the second interface in the second operating mode to receive digitally encoded information from a sensor connected to the second interface, to process this information and to pass this processed digitally encoded sensor information on to the first interface, wherein the second interface has a voltage source (Q1, Q2, U2, R903, R904), which delivers a predetermined voltage, and wherein the voltage source (Q1, Q2, U2, R903, R904) is designed to supply power to the sensor in the second operating mode, and a measuring circuit (R902, R901, R153) for measuring a voltage applied across the second interface, wherein the second interface is configured, in the second operating mode, to digitally receive the digitally encoded information from the connected sensor by detecting a clocked voltage change between two different voltages at the output of the second interface, wherein a first higher voltage and a second lower voltage of the second interface represent digital states of the digitally encoded information.