This unit is for fast programming of the märklin LokDecoder mLD3 and mSD3. You can connect it easily to your PC/laptop by means of a USB port. You will require the märklin Decoder Tool Software that can be downloaded easily on our homepage. The software will help you transfer existing sound or sound you have recorded on your own quickly and easily. You can now also program very easily all other settings such as maximum speed, braking behavior, etc.