Märklin now uses the Motorola format which was once limited to HO scale but now will operate all model railroad layout configurations. It is compatible with both 2-rail and 3-rail layouts and it will control either AC or DC powered locomotives. The older 1-Gauge system, used a "frequency modulated" data format, was used by Märklin since 1989 for 2-rail layouts with DC powered motors and is no longer being sold. The current 1 Gauge products are manufactured with the Motorola data format which Märklin has used in 3-rail layouts for both AC and DC trains since 1984.

The current Control Unit 6021 works with 1 Gauge and the 6017 Booster. Decoders for the 1 Gauge locos include:

6095 high-efficiency decoder - for normal use
86095 high-efficiency decoder - for two motor locomotives
66152 high-efficiency decoder - for the Class 323 "Köf"
66982 high-efficiency decoder - T3 (#5504)
6090 high-efficiency decoder - for 1 Gauge locos with restricted room

Also, don't forget the Maxi (65853) and DELTA (6603) decoders which are often used by 1 Gauge operators where no function control is necessary.