Method for controlling a multi-coloured signal arrangement having a multi-coloured LED, a connection to the power supply of the signal arrangement and a control input, comprising the following steps: - connecting the control input of the signal arrangement either to a control output of a first control unit for controlling the signal arrangement by means of PWM signals, wherein the first control unit is a programmable logic controller, or to a control output of a second control unit for controlling the signal arrangement by means of an asymmetric bus communication; - connecting a supply voltage U B to the signal arrangement via the connection to the power supply of the signal arrangement; - moving the signal arrangement, subject to a measured voltage U DI/Bus, into a BUS mode if the signal arrangement has been connected to the second control unit, or moving it into a PWM mode if the signal arrangement has been connected to the first control unit, wherein the signal arrangement in the BUS mode can be controlled by means of bus communication and the signal arrangement in the PWM mode can be controlled by means of PWM signals, characterised in that the method further comprises the following: - measuring the voltage U DI/Bus at the control input of the signal arrangement within a previously fixed time period Δt after the supply voltage has been connected, wherein the first control unit generates a first voltage at the control input of the signal arrangement within the time period Δt, and the second control unit generates a second voltage at the control input within the time period Δt, wherein the first voltage and the second voltage are different, wherein this is achieved by an appropriate programming of the first control unit and of the second control unit; wherein the control signals of the control unit (2, 3), connected to the signal arrangement are conducted in parallel to a UART input and to a digital input, DI input, of a microcontroller of the signal arrangement, and wherein in the BUS mode of the signal arrangement, the control signals are evaluated only via the UART input, and in the PWM mode of the signal arrangement, the control signals are evaluated only via the DI input. - connecting the control input of the signal arrangement either to a control output of a first control unit for controlling the signal arrangement by means of PWM signals, wherein the first control unit is a programmable logic controller, or to a control output of a second control unit for controlling the signal arrangement by means of an asymmetric bus communication; - connecting a supply voltage U B to the signal arrangement via the connection to the power supply of the signal arrangement; - moving the signal arrangement, subject to a measured voltage U DI/Bus, into a BUS mode if the signal arrangement has been connected to the second control unit, or moving it into a PWM mode if the signal arrangement has been connected to the first control unit, wherein the signal arrangement in the BUS mode can be controlled by means of bus communication and the signal arrangement in the PWM mode can be controlled by means of PWM signals, - measuring the voltage U DI/Bus at the control input of the signal arrangement within a previously fixed time period Δt after the supply voltage has been connected, wherein the first control unit generates a first voltage at the control input of the signal arrangement within the time period Δt, and the second control unit generates a second voltage at the control input within the time period Δt, wherein the first voltage and the second voltage are different, wherein this is achieved by an appropriate programming of the first control unit and of the second control unit; wherein the control signals of the control unit (2, 3), connected to the signal arrangement are conducted in parallel to a UART input and to a digital input, DI input, of a microcontroller of the signal arrangement, and wherein in the BUS mode of the signal arrangement, the control signals are evaluated only via the UART input, and in the PWM mode of the signal arrangement, the control signals are evaluated only via the DI input.