Shot clock
A shot clock is a timer designed to increase the pace (and subsequently, the score) in a competitive sport. The sport most identified with the shot clock is basketball, although other sports have used one (such as the play clock in both American football and Canadian football) or are considering implementing one of their own to shorten the length of time needed to play the game to completion.
History
Coach Howard Hobson, who coached at Oregon State University and later Yale University, is credited with the idea. It first came to use in 1954 in Syracuse, New York, where Danny Biasone, the owner of the NBA's Syracuse Nationals, experimented using a 24-second version during a scrimmage game. Biasone then convinced the NBA to adopt it. His team went on to win the 1955 championship.
Some say that this invention "saved the sport of basketball" as it had begun to lose fans before its inception. This was largely due to the stalling tactics used by teams once they were leading in a game. Without the shot clock, teams could pass the ball nearly endlessly without penalization. Very low-scoring games were common.
When the shot clock first came into play, it made many players nervous, to the extent that the clock hardly came into play, as players were shooting much quicker than twenty seconds.
Basketball
In professional men's basketball (both NBA and FIBA), the shot clock counts down 24 seconds, thus often being called the "24-Second Clock." Failure to attempt a shot that hits the rim within this time results in loss of possession. A buzzer goes off when the shot clock reaches zero. A shot attempted right before this buzzer is called a buzzer beater.
The shot clock has been criticized as teams occasionally foul intentionally so the opposing team cannot use the full 24 seconds. Thus the losing team might have a chance at coming back and tying or winning the game.
Danny Biasone came up with 24 seconds by dividing 2,880 (the number of seconds in a game) by 120 (the average number of shots in a game at that time).
Women's basketball, both college and professional, uses 30 seconds. Men's college basketball in the United States uses a 35-second clock.