to locomotives lacking the additional switched functions (i.e. c90 equipped locomotives). Function decoders require their own address from the 80 addresses available for locomotives (the address can be shared with another decoder lacking additional functions). Märklin had offered some special models with additional functions for the original digital system, but separate function decoders only became available with the enhanced system. DELTA A simplified system intended to appeal to beginners and those put off by the then substantial cost of full digital systems, DELTA offered control of up to four locomotives simultaneously. DELTA decoders did not have motor regulation and initially lacked any way of easily changing the address. DELTA has now been discontinued, simplified digital controllers & decoders are offered instead (Mobile Station & 36xxx series locomotives). Early DELTA controllers lacked the Function / Off buttons and c80 Digital models running on DELTA had Function permanently on which affected any such models equipped with TELEX remote couplers. c90 models running on DELTA had Function permanently off. Märklin Digital (mfx) In 2004 the completely new Märklin Systems digital control was unveiled. A new two way protocol can control up to 65,000 digital devices, each locomotive can have up to 128 speed steps and 16 functions. Developed by ESU with all components initially made by them for Märklin, later the name "Märklin Systems" was dropped and once again the system is known as "Märklin Digital". Introduced in 2013, the extended mfx+ digital control system provides additional locomotive parameters and allows feedback with mfx+ equipped locomotives. The virtual fuel state of each mfx+ equipped locomotive can be set and monitored. For steam locomotives, additional parameters such as boiler pressure and fire state can be set, monitored, and controlled. Eventually, the locomotive must return to a fuelling point for replenishment (feedback modules denote the fuelling points). Signals may also be fitted with feedback modules, requiring acknowledgement by the operator as the train passes, just as in real operation. The new controller software provides a cab view of the locomotive to allow control of all parameters. This gives a computer simulation view of the locomotive while controlling a model. Controllers The Central Station 60212 had two locomotive controllers built in and a large monochrome LCD screen with graphical display and descriptive names for locomotives. The controller stored a database of pre-mfx digital locomotives with their functions so that they may be easily set up (mfx