Although new decoders rarely are defective you occasionally run across a circumstance where you might want to test a decoder before installing it in your model locomotive. In this video I'll share with you a look at a commercially available decoder tester, show you the types of decoders it can be used with, and then give you a working demonstration with a couple different types of decoders. Finally I'll add my own thoughts on when you might want to test decoders.