from just two wires to the track, but in practice multiple feeds will be required and power to the track is usually separated from power to accessories. The final step to ideal running was the development of motor regulation or speed control (often misleadingly called "load control"). Locomotive motors are controlled using pulse-width modulation which gives much better regulation than conventional analogue control. Additionally, utilizing the full track power available, decoders can use motor feedback and constant adjustment to maintain steady speed regardless of train load or track gradient. Combined with braking and acceleration delay (artificial inertia) these decoders give smooth and exact speeds with reliable slow speed control. A number of different digital systems were developed, but Märklin Digital and DCC (Digital Command Control) are the two main systems on the market. The systems are electrically compatible and some controllers can simultaneously control both types of decoder. Märklin offered versions of their original digital system for 2-rail users. Märklin Digital Märklin first presented the new digital control system at the Nürnberg Toy Fair in 1979. The Motorola based system was officially introduced in 1985, developed by a relatively unknown electronics contractor with most components built by Märklin. In subsequent years, another contractor, Bernd Lenz, would also work on the system producing locomotive decoders and, later, Märklin's first DC command control offering. This first DC offering was later developed into what is now known as Digital Command Control (DCC). The new Märklin Digital system offered simultaneous control of up to 80 locomotives and 256 accessories. 14 locomotive speed steps (stop 0 and 1 - 14) were provided and an accessory "Function" that was used for locomotive front and rear headlights or TELEX remote uncoupling. Electronics of the time were relatively expensive and the system used ternary logic to reduce the number of components and cost of devices. Early decoders cost as much as many model locomotives and the expense of upgrading an existing layout was considerable. Controllers The original 6020 Central Unit provided track power & generated locomotive commands but required a separate 6035 locomotive Control 80 with speed controller, keypad for decoder address, Function / Off buttons, and Start / Stop buttons to switch track power. The red Stop button was provided as an emergency stop to immediately halt all trains. A two digit display showed the selected locomotive address (01 - 80). Solenoid devices, such as turnouts, were