Abstract: Apparatus for controlling the electrical functions in a plurality of different locations of a vehicle comprises a plurality of electrical control units connected to a data bus (23) and distributed throughout the vehicle. All control units are identical and all are programmed to carry out all the electrical functions of the vehicle. Each unit incorporates means to detect the resistance at the point at which it is connected into the circuitry and to compare that resistance with the stored table of resistance and to select on the basis of that comparison the program for operation appropriate to the particular location in which the unit is disposed. In this way only one unit needs to be certified and units may be switched from location to location to provide a "get you home" service should one of the units fail in a particularly critical location.