This decoder is for converting Märklin/Trix H0 locomotives with built-in high-efficiency motors or other DC motors. The märklin SoundDecoder3 has a wiring harness soldered to it with an eight-pin NEM interface connector plug for installation in many locomotives with the appropriate NEM interface connector and locomotives with a lack of space.

The märklin LokDecoder3 supports the digital formats mfx, MM1, MM2, and DCC. The decoder has preset sound for a steam locomotive.