Soundtraxx Sierra Overview Many people over the years just knew this product as the Sierra, and not from the parent company Soundtraxx, most known by the Tsunami, a very successful DC/DCC sound and motor decoder, the first all in one decoder that changed the sound based on actual motor load, via BEMF. The Sierra is an "old school" DC only sound system, that sounded good, but was a pain to program, and also often needed extra electronics when run by a PWM motor driver, and also often needed special eletronic isolation to run sound triggers from an R/C system. Still, many people still love them and used ones are relatively plentiful. Notes: One thing that is very important, this unit requires fixed polarity, it cannot be connected directly to the rails in a normal DC system. The manual is not clear on this, but if you look at the wiring diagrams that show ACTUAL track power circuits, you will see a full wave bridge rectifier between the track and the Sierra. Also, there is no listing in the manual for all the screw terminals. There is a very problematic connector for the battery, and you can use the screw terminals instead. This is NOT in the manual, but it's true, Terminal 2 is ground and Terminal 4 is positive. You can kind of verify this by seeing that terminal 2 is used for the volume up down control, bringing terminals 1 or 3 to ground. You can also see terminal 4 is the common for lights, and this is normal in DCC decoders, the common for lights is actually positive.