A circuit component between a first pole and a second pole of a potential, wherein the circuit component is provided for switching between a light source and an additional light source of a signalling device, comprising: - a first and a second switching device (3, 4) each of which comprises a two-pole current connector, at least one switch and a function for closing at least one switch, when the current flows in one direction through the two-pole current connector, - a first and a second connection device (5, 8), each of which comprises a signal input, an output, a first connection pole, a second connection pole and a function for the connection between the output and either the first or the second connection pole (11, 21) in dependence of a logic level at the signal input, - switching the current connector of the second switching device between the outputs of the first and second connection devices (5, 8), - switching the current connector of the first switching device between the second connection pole of the first connection device and the second pole, - a first switching function for energising the current connector of the second switching device with the connection between the output and the second connection pole of the first connection device and with the connection between the output and the first connection pole of the second connection device and where a series connection is provided between the first and second poles (1, 2), which comprises the current connectors, characterised in that - a unit for voltage inversion is provided between the second connection pole of the first connection device and the first connection pole of the second connection device, which in the first switching function is switched for short-circuiting the current connector of the first switching device in the series connection, and in a second switching function is switched for energising the current connector of the first switching device. - a first and a second switching device (3, 4) each of which comprises a two-pole current connector, at least one switch and a function for closing at least one switch, when the current flows in one direction through the two-pole current connector, - a first and a second connection device (5, 8), each of which comprises a signal input, an output, a first connection pole, a second connection pole and a function for the connection between the output and either the first or the second connection pole (11, 21) in dependence of a logic level at the signal input, - switching the current connector of the second switching device between the outputs of the first and second connection devices (5, 8), - switching the current connector of the first switching device between the second connection pole of the first connection device and the second pole, - a first switching function for energising the current connector of the second switching device with the connection between the output and the second connection pole of the first connection device and with the connection between the output and the first connection pole of the second connection device and where a series connection is provided between the first and second poles (1, 2), which comprises the current connectors, - a unit for voltage inversion is provided between the second connection pole of the first connection device and the first connection pole of the second connection device, which in the first switching function is switched for short-circuiting the current connector of the first switching device in the series connection, and in a second switching function is switched for energising the current connector of the first switching device.