With Tamiya the battle system is part of the electronics. They all have it, so all you have to do is add the apple and you are in business. And yes the Tamiya apple MSRP is around $75.00. You can buy a DBU from Darkith for $15.00 and they work fine with the Tamiya system. However you then end up with a bunch of issues at a club meet. The Darkith unit with its four sensors is more sensitive and puts you at a slight disadvantage. I use a TBU(Tamiya Battle Unit) with my Darkith systems to reduce the differences to a minimum.