In drag racing

Drag racing

Drag racing is a competition in which specially prepared automobiles or motorcycles compete two at a time to be the first to cross a set finish line, from a standing start, in a straight line, over a measured distance, most commonly a ¼-mile straight track....

, a transbrake is a mechanism that selectively places the transmission in first and reverse gear

Gear

A gear is a rotating machine part having cut teeth, or cogs, which mesh with another toothed part in order to transmit torque. Two or more gears working in tandem are called a transmission and can produce a mechanical advantage through a gear ratio and thus may be considered a simple machine....

s simultaneously, effectively holding the race car stationary as if the foot brake was applied. The transbrake is activated by the driver by applying electrical current to a solenoid

Solenoid

A solenoid is a coil wound into a tightly packed helix. In physics, the term solenoid refers to a long, thin loop of wire, often wrapped around a metallic core, which produces a magnetic field when an electric current is passed through it. Solenoids are important because they can create...

 at the transmission. With the transbrake engaged (transmission locked), the engine

Engine

An engine or motor is a machine designed to convert energy into useful mechanical motion. Heat engines, including internal combustion engines and external combustion engines burn a fuel to create heat which is then used to create motion...

 throttle

Throttle

A throttle is the mechanism by which the flow of a fluid is managed by constriction or obstruction. An engine's power can be increased or decreased by the restriction of inlet gases , but usually decreased. The term throttle has come to refer, informally and incorrectly, to any mechanism by which...

 can be increased to any position (opening) in preparation for launch without the race driver worrying about the car creeping forward. Milliseconds before the green light illuminates on the Tree

Drag racing

Drag racing is a competition in which specially prepared automobiles or motorcycles compete two at a time to be the first to cross a set finish line, from a standing start, in a straight line, over a measured distance, most commonly a ¼-mile straight track....

 the transbrake is released (by the driver releasing an electrical switch or by a delay box

Delay box

"Delay Box" is a common slang term used in drag racing to describe an on-board timer which is a Transmission Brake Delay Timer. A transbrake forces the race car to remain stationary at the starting line, in gear, regardless of how much engine power is applied. When the visual signal is given to...

 "timing out" originally triggered by the driver releasing an electrical switch) and the car launches forward, its engine already in the higher power band

Power band

The power band of an engine or electric motor refers to the range of operating speeds under which an the engine or motor is able to operate efficiently...

and the transmission already in low gear. It was invented by Billy Whatley in the year 1973.