The Hawk-Eye system is extensively used in tennis, using cameras to calculate the trajectory of the ball.

CNN: Does football need technology?

Like the Hawk-Eye system it uses a computer to send a signal to the referee's watch when a goal is scored.

CNN: Does football need technology?

The Hawk-Eye system uses strategically-placed cameras to determine the exact flight of a ball and is already used in international cricket and at grand slam tennis tournaments.

CNN: Goal-line technology enters final testing

The International Football Association Board (IFAB) said that two technologies -- the British-designed "Hawk-Eye" system and German one called "GoalRef" -- will be trialed between now and June before a final decision is made in July.

CNN: Goal-line technology enters final testing

In tests last year at Yankee Stadium and Citi Field, MLB experimented with the Hawk-Eye animation system that is used to judge line calls in tennis and the TrackMan radar software used by the PGA Tour.

WSJ: MLB hoping for large replay expansion in 2014

Hawk-Eye's system uses seven cameras to track the movement of the ball and sends a signal -- within a second -- to watches worn by match officials when a goal is scored.

CNN: England on course for goal-line history

The controversial Hawk-Eye ball-tracking system, which was developed in England and can accurately call LBWs (leg before wickets), catches and run-outs, is now used in other sports, including tennis.

CNN: Tech puts cricketers on right lines

At the top of that list is Hawk-Eye, the ball tracking system already used in tennis and cricket that may soon stake its place in World Cup soccer.

FORBES: The Sports Names You Need To Know In 2013

While both CAIROS and GoalRef use magnetic fields around the goal and need to insert a chip in the ball, Hawk-Eye and GoalControl use a 3D imaging system to determine the precise location of the ball.

CNN: Latecomer wins FIFA goal-line tech deal

Using similar technology, Hawk-Eye Innovations, based in England, has developed a football system to determine if a goal has been scored.

CNN: Does football need technology?

However, both GoalRef and Hawk-Eye's technology must now pass a stadium test before either system can be used in a match.

CNN: FIFA awards goal-line technology licenses

As I understand it, the 'Hot Spot' people charge more for their system when DRS is in place, while Hawk-Eye does not.

BBC: Jonathan Agnew column

There is also less opportunity for using Hawk-Eye for in-game analysis - the original use of the system when it was launched as parts of Channel 4's cricket coverage in 2001.

BBC: Hawk-Eye's inventor eyes football expansion

Hiroshima, who won the Japanese championship for the first time last month to earn their place in football history, will also take part as the second system is used, with camera-based Hawk-Eye being used for Sunday's tie with the seven-time African champions.

CNN: World football enters technological era