Oh boy first post.
As far as I am aware the IFF system for the Viggen is not currently implemented, and probably won't be unless ED decides to expand the game's IFF mechanics. Unfortunately, that hasn't prevented me from agonizing over what the cockpit controls for the IFF system are and how they work. So I've been scouring the forum trying to dig up as much information as I could on the Viggen's IFF, and there isn't much. However I think I've been able to piece together what the IFF/transponder panel actually does, and I would appreciate a sanity check.
According to the current revision of the Heatblur Viggen manual, page 26, the red box is called the "transponder control panel" and the blue circle is called the "IFF control panel". Later in the manual, page 41-42, the blue circle is referred to as the "IFF transponder indicator". This heavily implies to me that the IFF system is separate from a transponder system, and given the panel's layout said transponder is a standard 4 digit system like you would find in any modern commercial aircraft.
This is further supported by Toertchen's translations of the checklists from the actual aircraft manual. In the startup checklist there are separate steps for the IFF radio and the transponder, where the IFF radio is turned on but the transponder is kept off, which suggests they are two different things. I have no idea how to turn the IFF radio on if this is the case though, as I can't find a separate switch for it.
Does anyone else know anything about the IFF/transponder system?