Running out the clock
In American football, each quarter of a game is measured with a 15-minute game clock, or 12-minute clock in many high school football codes and the German Football League. A team in possession of the lead and the ball will attempt to use up as much of the game clock as possible in order to bring the game to an end more quickly, thus denying the opposition another chance on offense.
Scoreboard
In both the United States and Canadian football codes, the minimum details displayed are the time and score of both teams. A typical high school scoreboard will additionally display the down, the yardage of the line of scrimmage, the yards to go until a first down, the team with the possession (usually signified with the outline of a football in lights next to the possessing team's score) and the quarter. Higher levels will also include play clocks and the number of time outs left for each team. American football scoreboards may include a horn to signal the end of a quarter, but they are not used in larger venues. In those cases, the referee or public address announcer denotes the termination of a quarter vocally via the PA system; formerly quarter ends were denoted with the firing of a starting pistol in the era before digital timing.