This profile standardizes the electronic interfaces of the add-on equipment for special-purpose passenger cars such as taxis, police cars, emergency vehicles, vehicles for handicapped persons etc. Use of CiA 447 allows the car manufacturer to choose appropriate add-on devices (e.g. taximeter, roof bar, camera) from diverse suppliers. Standardized interfaces simplify the integration of the add-on devices based on the plug-and-play principle. Development effort, time and costs are minimized. The effort for testing and for authorization of special add-on devices is reduced. Vehicle manufacturers do not require additional agreements with device suppliers.