The Blinovitch Limitation Effect limiter was a Time Lord device that limited the effects of the Blinovitch Limitation Effect, making it safer for one to meet their earlier selves.
The third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, eleventh, twelfth and thirteenth incarnations of Drax conned the Fourth Doctor into stealing the limiter, which was what allowed them to cooperate on this scheme in the first place. (AUDIO: The Trouble with Drax)