Decoder for controlling up to 4 auxiliary functions (f1 to f4) from the Control Unit (6021), a Control 80 f locomotive controller connected to this central unit, or the Interface. This function decoder can either be installed in locomotives along with a locomotive decoder or by itself in cars. It can be coded for 80 different addresses. When sufficient space is available, any Märklin digital locomotive or any locomotive with a built-in Delta module can be equipped with additional controllable functions such as a smoke unit or Telex couplers (where the locomotive already has these couplers). On passenger cars interior lighting can be a controllable function.