There is no such thing as a "CAM card reader".
It is a card reader. It is for the old TM1000 models that didn't have a reader. It basically coverts it into a tm1000+ and will read Conax cards, and a few others with receiver patches.
I bought one from the same seller for about £12, it took ages to come, and wasn't initially supplied with the metal bracket to hold the thing in place, but a phone call to him got it sorted.