Fostech binary trigger
18 U.S.C. 922(o): Transfer or possession of machinegun 26 ...
pull of the trigger, initiates an automatic firing cycle that continues until either the finger is released or the ammunition supply is exhausted, is a machinegun under the National Firearms Act, 26 U.S.C. 5845(b), and the Gun Control Act, 18 U.S.C. 921(a)(23).