The timekeeper (or timekeepers) have varying responsibilities depending on the equipment available. A chronometer is a portable timekeeper that meets certain precision standards. They are assisted by a timekeeper and a scorekeeper. The referee, ring announcer, timekeeper and commentators were midget versions of regular personnel. The officials included a referee and timekeeper. Seiko was the official timekeeper of the North American Soccer League during the 2014 season. The four main categories are&colon; referee, secretary, timekeeper and goal judge. Longines served as the official timekeeper of the games. The weakest link of any mechanical timekeeper is the escapement's lubrication. Previous explanations of the prokaryotic circadian timekeeper were dependent upon a DNA transcription/translation feedback mechanism. These umpires are often assisted by a technical bench including a timekeeper and record keeper. A game consists of four quarters and a timekeeper officiates their duration. In 2014 Omega became the official timekeeper of the 2014 Sochi Winter Olympics. Witnesses are sworn in by their team's bailiff/timekeeper. Omega is also the official timekeeper for the 2012 Summer Olympics.