<Li> The offense may attempt to re-advance the ball into the opponent's end zone for a two - point conversion worth 2 points . </Li> <P> While the opposing team has possession, the defense attempts to prevent the offense from advancing the ball and scoring . If an offensive player loses the ball during play (a fumble) or the ball is caught by a defensive player while still in the air (an interception), the defense may attempt to run into the offense's end zone for a touchdown . The defense may also score points by tackling the ball carrier in the offense's own end zone, called a safety (which is worth two points). </P> <P> Collegiate and professional football games are 60 minutes long, divided into four quarters of 15 minutes each . In high school football, 12 minute quarters are usually played . The clock is stopped frequently, however, so that a typical college or professional game can exceed three hours in duration . The referee controls the game clock and stops the clock after any incomplete pass or any play that ends out of bounds . In addition, each team is allowed 3 timeouts in each half that they may use at their own discretion . </P> <P> The clock may also be stopped for an officials' time - out, after which, if the clock was running, it is restarted . For example: if there is a question whether or not a team has moved the ball far enough for a first down, the officials may use a measuring device (the chains) to determine the distance . While this measurement is taking place, the officials will signal for a stoppage of the clock . Once the measurement is finished and the ball is placed at the proper location (spotted), the referee will then signal for the clock to restart . Additional situations where officials may take a time - out are to administer a penalty or for an injured player to be removed from the field . </P>

How many timeouts do you get in the nfl