I've noticed looking around that there are some second hand TIU's with Protosound 2 printed on the front instead of DCS. Is there a difference between the two and will PS3 locomotives work with a protosound 2 TIU? Thank you very much for any advice you can offer!
Yes they will work with older TIUs. The older versions may need filters or bulbs attached to work better.
The newer version L TIUs with the USB port have better signal output.
The first two versions of the TIU that had the "ProtoSound 2" logo. The original Rev. G TIU should generally be avoided. The biggest issue is that the Rev. G has no internal fuses. You have to provide your own external fact acting fuses or circuit breakers, or only use a Z-4000 transformer. There are some other internal weaknesses that make them more prone to failure. The second version, the Rev. H1, also had the "ProtoSound 2" logo. The H1 has internal blade fuses and several other internal improvements. The Rev. G's and H1's are 18 and 17 years old respectively. A fully funtional H1 for less than a $100 can be a real bargain, especially if you're looking for a backup or bench testing TIU.
Every TIU ever made will work with the latest firmware, all PS2 and PS3 engines, the WIU and the DCS App. There are no totally obsolete TIU's, but the Rev. L (released in late 2010) are definitely the best of the bunch.