Fully automatic time (abbreviated FAT) is a form of race timing in which the clock is automatically activated by the starting device, and the finish time is either automatically recorded, or timed by analysis of a photo finish. The system is commonly used in track and field as well as horse racing, dog racing, bicycle racing, rowing and auto racing. In these fields a photo finish is used. It is also used in competitive swimming, for which the swimmers themselves record a finish time by touching a touchpad at the end of a race. In order to verify the equipment, or in case of failure, a backup system (typically manual) is usually used in addition to FAT.
 TechnologyIn races started by a starting gun, a sensor is typically attached to the gun which sends an electronic signal to the timing system when fired. Alternatively, a starting light or sound which is electronically triggered (such as a horn), the system is typically also wired to the timing system. In sports that involve a finish line that is crossed (rather than a touch finish, as in swimming), the current finishing system is a photo finish which is then analysed by judges.
The current photo-finish system used in Olympic competition, as well as other top-level events uses a digital line-scan camera aimed straight along the finish line. FinishLynx and Omega are examples of commercial timing systems commonly used in athletic competitions. These cameras have an image field only a few pixels wide, with a single frame forming a narrow image only of the finish line, and anything which is crossing it. During a race, the camera takes images at an extremely high frame rate (the exact rate depends on the system, but can be in the thousands of frames per second). Computer software then arranges these frames horizontally to form a panoramic image which effectively displays a graph of the finish line (and anything crossing it) as time passes, with time denoted on the horizontal axis.
Before the advent of digital photography, (and still available as an alternative), a similar film-based system was used, consisting of a slit which a strip of film is advanced past at a constant rate to produce a similar panoramic image to the digital system. Less-expensive video-based systems also exist; however, VHS and SVHS frame rates limit the timing precision that can be achieved by these media.
There are also similar timing systems that use the simple process of breaking a beam of light. While such systems are frequently used to provide instant results (for the media), the object they are timing is more difficult to define.
 Use in athletics
An example of a photographic automatic timed race: Sabine Busch , right, wins with 53.24s and Cornelia Ullrich comes second with 53.55s.According to the IAAF, any record in athletics (world, Olympic, or national) or qualifying time for Olympic Games or World Championships set in a sprint event must be timed by a FAT system to be valid.
Hand times, those with humans operating the stopping and/or starting mechanisms are highly prone to error. By rule, they are only accurate to a tenth (.1) of a second, all 100ths of a second beyond zero must be rounded to the next highest tenth.
Many track and field statisticians use a conversion factor estimate of 0.24 seconds added to any hand-timed mark in the 100 m or 200 m event, and 0.14 seconds to any hand-timed mark in the 400 m or longer event. These conversion factors are only applicable for comparing marks from a variety of sources, but are not acceptable for Record purposes. In the case of comparing an adjusted manual time to FAT timing, an original FAT time being equivalent, the FAT time will be considered more accurate, and thus the athlete will be given the higher seed, or comparison ranking. This old method of converting times dates back to when FAT systems were much less common. They are increasingly less acceptable even at low level meets and certainly not at the upper level of the sport.
Above from Wikipedia.
Times are always rounded up to the nearest 10th. E.g. 10.50s would be 10.5s but 10.51 would be 10.6s.
If 1 stop watch is used e.g. 10.51, then the final time is 10.60.
If 2 stop watches are used, e.g. 10.51 and 10.69 then the slower time is the final time 10.70.
If 3 stop watches are used, e.g. 10.50, 10.54, and 10.69 then the middle time is the final time 10.60.
Note on national records
Even though hand timing is not used for record keepign purposes for most countries. PATAFA still keeps a list of hand timed national senior and junior national records. The instances were this maybe seen as acceptable is for events of 800m or more when the differentials in timing are not as great, and if a record was set in the days before electronic timing was available in sprint events e.g. pre 1980s.