Play clock

A play clock (also called a delay-of-game timer) is a timer designed to increase the pace (and subsequently, the score) in American football and Canadian football, similar to what a shot clock does in basketball. The offensive team must snap the ball before the time expires, or else they will be assessed a 5-yard delay of game (American football) or time count violation (Canadian football as "delay of game" is a different offense) penalty. If a visible clock is not available (or not functioning), game officials on the field will use a stopwatch or other similar device to enforce the rule.
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