Interface circuit for operating a light source, equipped with - a first pair of input terminals and a second pair of input terminals for connection to lamp connection terminals of an electronic fluorescent lamp driver, - a first string comprising a series arrangement of first two resistors, conductive interconnecting a first pair of input terminals, - a second string comprising a series arrangement of second two resistors, conductive interconnecting a second pair of input terminals, - a third string, conductive interconnecting a first terminal of the first string and a second terminal of the second string, wherein a common terminal of the resistors comprised in the first string forming the first terminal and a common terminal of the resistors comprised in the second string forming a second terminal, wherein - the third string comprises a rectifier, output terminals of said rectifier being coupled, during operation, to the light source, and a first switching element for controlling the conductive state of the third string, - a fourth string coupled to the third string and comprising a sensor circuit, having an output terminal coupled to a control electrode of the first switching element, wherein the sensor circuit is arranged to sense the amplitude of a high frequency AC voltage between the first and the second terminal (T1, T2) and for rendering the first switching element conductive when the amplitude of the high frequency AC voltage reaches a predetermined value, and characterized in that the interface further comprises a fifth string comprising an impedance and a further switching element, wherein a control electrode of the further switching element is coupled to the output terminal of the sensor circuit and wherein the fifth string is coupled between output terminals of the rectifier or in parallel to the third string. - a first pair of input terminals and a second pair of input terminals for connection to lamp connection terminals of an electronic fluorescent lamp driver, - a first string comprising a series arrangement of first two resistors, conductive interconnecting a first pair of input terminals, - a second string comprising a series arrangement of second two resistors, conductive interconnecting a second pair of input terminals, - a third string, conductive interconnecting a first terminal of the first string and a second terminal of the second string, wherein a common terminal of the resistors comprised in the first string forming the first terminal and a common terminal of the resistors comprised in the second string forming a second terminal, - the third string comprises a rectifier, output terminals of said rectifier being coupled, during operation, to the light source, and a first switching element for controlling the conductive state of the third string, - a fourth string coupled to the third string and comprising a sensor circuit, having an output terminal coupled to a control electrode of the first switching element, wherein the sensor circuit is arranged to sense the amplitude of a high frequency AC voltage between the first and the second terminal (T1, T2) and for rendering the first switching element conductive when the amplitude of the high frequency AC voltage reaches a predetermined value, and