Right, I've managed to get it going off the makita batteries. The third pin appears to need to be pulled low through a resistance (I had 10k in there, but not sure what the significance of it is), I tried bridging it without the resistance and didn't get anything. Its clearly for battery protetcion because if you have it pulled low and run it, then disconnect the resister, it'll stop, but won't start again again if you reconnect untill you press the trigger again.
Looking on the net, the makita batteries work in sort of the opposite way, the third pin is held high until the battery voltage has dropped too low then it either goes low or floating, it shouldn't be too difficult to map this across with an NPN transistor and a couple of resisters, I'll have a bit more of a play later on, but I'm guessing if you are able to have a look at printing an adapater that has a small amount of space in the middle? The power connections can be solid rails, but you'd need a point at which you could tap off with a small CSA wire to the space in the middle. If its possible it might be worth while doing it as a separtae adapater, rather than a screwed conversion, as should then be able to be used with any of the parkside tools
