So one of the issue with Tamiya IR emitter is that they only shipped with a TBU, Tamiya provides a unique mount for each of its tank because it is barrel mounted and is different from tank to tank. The problem is that there isn't enough of these to go around as most of us don't have one set of TBU/IR emitter for each of our tanks (Of course Tamiya expect that but it is simply too stupid). Moreover ,these mounts are too tight for the barrel and they usually ended up scratching the nicely finish metal barrel.
So I have been trying different solutions but then I discover that the standard 2mm JST plug with some trimming will actually fit the Tamiya connectors (which I believe are molex) as they have the same 2mm pin spacing.
To make a long story a little shorter, I have now starting to fit DIY IR emitter on my Tamiya tanks without using the butt ugly barrel clips, and during my testing of these new IR emitter, I was reminded again about this little Tamiya quarks. Unless a TBU is plugged into the base, the IR emitter will not function. I guess this makes sense if you think about it, as you cannot have a tank that does not have a TBU (i.e. Take hits) starting hitting other tanks on the field.
None of the other after market boards actually has this "feature".