This device is for fast testing of the new märklin LokDecoder3 and märklin SoundDecoder3 as well as all other decoders that use the following interface connections: NEM 651, NEM 652, MTC14, MTC21 and PluX22. Other decoders such as for 1 Gauge, LGB, or those with individual wires must be connected with set screw terminals.Other features include:- LED monitoring for the peak signal, for Aux 1-6, track input, Aux 3, and 4 amplified and not amplified.- Track connections for the digital central controller.- Speaker.- Motor- Separate terminal clips for another motor.- Direct connections to the märklin Decoder Programmer.