Question: " I checked the identification CV's and it shows mfgr. 153 (TCS) and model number 39. I ran the latest DecoderPro against it and it came up as an A4X. Is there a diff model number in the CV's for these two decoders? Is it possible that the one I have was set to a model number 39 at the factory and that is an error?" - your customer. Answer: There is not a difference in the model number for these decoders so DecoderPro really has no way of knowing the difference between an A4X and a T4X. They both have identical features. CV7 is not really a model number, rather it is a version number. We use it to designate software revision levels. When a software revision is made to the TCS line it is made to all of the decoder lines and not a particular model. If decoder pro does not recognize the TCS decoder, use any of the default TCS decoder profiles and it will successfully program the decoder.