Delay box is a device used in drag racing, allowing a racer to launch the vehicle with the same reaction time on every pass. This device requires a transbrake in order to function, and sometimes a two-step rev limiter is also used. Before pulling up to the "Christmas Tree" as the group of lights at the beginning of the racetrack is known, the racer dials in how long it will take for the tree to countdown to the green lights. This time is set in the delay box and the racer then readies himself for the first yellow light to appear on the tree by holding down the switch which arms the delay box and pressing the accelerator to the floor. When the first yellow comes on, the racer releases the switch for the delay box, and the device begins a countdown at the same time as the tree, releasing the transbrake (and canceling the first stage rev limiter, if used) at the same time as the tree flashes green.