The tandem rating system in the USA is such that each manufacturer issues their own Tandem Instructor rating.
You need a UPT rating to jump a Sigma and/or Vector tandem system, a Strong tandem rating to jump a Strong tandem rig and a rating from JumpShack to jump a Racer system.
If you need multiple ratings you can get cross trained to another tandem system after you have at least 25 jumps on one system. The manufacturer must approve the rating you have. Crosstrain is a shorter process to get the rating. Less examination jumps are required.If you need two ratings right away, it requires two full tandem rating courses for each rating.
USPA groupmember dropzones require all tandem instructors to hold the USPATandem Instructor rating in addition to the factory rating. Please go to the pages for each rating for more detailed information.