Referee: The referee has full control and authority over all officials. The referee will enforce all rules and decisions of FINA and shall decide all questions relating to the actual conduct of the meet, and event or the competition, the final settlement of which is not otherwise covered by the rules. The referee takes overall responsibility for running the race and makes the final decisions as to who wins the competition. Referees call swimmers to the blocks with short blasts of his or her whistle. This is the signal for the swimmers to stand next to their blocks. Starters call missing swimmers if necessary. Then the referee will blow a long whistle that will tell the swimmers to step on the block. For backstroke otherwise known as backcrawl events, the long whistle is the signal for the swimmers to step in the water. The referee will then blow another long whistle, signaling the swimmers to grab the gutter or the provided block handle (for backstoke/backcrawl events only). The referee will then hand over control to the starter. Starter: The starter has full control of the swimmers from the time the referee turns the swimmers over to him/her until the race commences. A starter sends the swimmers off the blocks and may call a false start if a swimmer leaves the block before the starter sends them. Clerk of course: The clerk of course assembles swimmers prior to each event, and is responsible for organizing ("seeding") swimmers into heats based on their times. Heats are generally seeded from slowest to fastest, where swimmers with no previous time for an event are assumed to be the slowest. Timekeepers: There are three timekeepers for each lane. Each timekeeper takes the time of the swimmers in the lane assigned to him/her. Unless a video backup system is used, it may be necessary to use the full complement of tim keepers even when automatic officiating equipment is used. A chief timekeeper assigns the seating positions for all timekeepers and the lanes for which they are responsible. The chief timekeeper collects from the timekeepers in each lane a card showing the times recorded and, if necessary, inspect their watches. One timer will be timing with a stopwatch, another recording it down, and one making sure everything is valid. Inspectors of turns: One inspector of turns is assigned to each lane at each end of the pool. Each inspector of turns ensures that swimmers comply with the relevant rules for turning as well as the relevant rules for start and finish of the race. Inspectors of turns shall report any violation on disqualification reports detailing the event, lane number, and the infringement delivered to the chief inspector of turns who will immediately convey the report to the referee. Judges of Stroke: Judges of stroke are located on each side of the pool. They ensure that the rules related to the style of swimming designated for the event are being observed, and observe the turns and the finishes to assist the inspectors of turns. Finish judges Finish judges determine the order of finish and make sure the swimmers finish in accordance with the rules (two hands simultaneously for breaststroke and butterfly, on the back for backstroke, etc.) If an official catches a swimmer breaking a rule concerning the stroke he or she is swimming, that swimmer is said to be disqualified (commonly referred to as a "DQ") and the swim is not considered valid. The referee can disqualify any swimmer for any violation of the rules that he personally observes. The referee may also disqualify any swimmer for any violation reported to him by other authorised officials. All disqualifications are subject to the decision of the referee.