A scoreboard is a large board for publicly displaying the score in a game. Most levels of sport from high school and above use at least one scoreboard for keeping score, measuring time, and displaying statistics. Scoreboards in the past used a mechanical clock and numeral cards to display the score. When a point was made, a person would put the appropriate digits on a hook. Most modern scoreboards use electromechanical or electronic means of displaying the score. In these, digits are often composed of large dot-matrix or seven-segment displays made of incandescent bulbs, light-emitting diodes, or electromechanical flip segments. An official or neutral person will operate the scoreboard, using a control panel.
Technology
Prior to the 1980s most electronic scoreboards were electro-mechanical. They contained relays or stepping switches controlling digits consisting of incandescent light bulbs. Beginning in the 1980s, advances in solid state electronics permitted major improvements in scoreboard technology. High power semiconductors such as thyristors and transistors replaced mechanical relays, light-emitting diodes first replaced light bulbs for indoor scoreboards and then, as their brightness increased, outdoor scoreboards. Light-emitting diodes last many times as long as light bulbs, are not subject to breakage, and are much more efficient at converting electrical energy to light. The newest light emitting diodes can last up to 100,000 hours before having to be replaced. Advances in large-scale integrated circuits permitted the introduction of computer control. This also made it cost effective to send the signals that control the operation of the scoreboard either through the existing AC wires providing power to the scoreboard or through the air. Powerline modems permit the digital control signals to be sent over the AC power lines. The most common method of sending digital data over power lines at rates less than 2400 bits per second is called frequency shift keying (FSK). Two radio frequencies represent binary 0 and 1. Radio transmission such as FSK sends data digitally. Until recently radio transmission was subject to short range and interference by other radio sources. A fairly recent technology called spread spectrum permits much more robust radio control of scoreboards. Spread spectrum, like the name implies, distributes the signal over a wide portion of the radio spectrum. This helps the signal resist interference which is usually confined to a narrow frequency band.
Scoreboards in various sports
North American football
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.
Basketball
A basketball scoreboard will at the minimum display the time left in the period and both teams' scores. The last minute of each quarter is usually displayed with tenths of a second, which is required in FIBA, NBA (since 1989), and NCAA (since 2001). Most high school scoreboards also include a display of the number of team fouls, the number of the last player to commit a personal foul (with the total number of personal fouls for that player), the period, and indicators of which team is in the team foul penalty situation, and possession (with a separate possession arrow display at half-court; not used in the NBA). College basketball scoreboards include shot clocks and the number of time-outs left for each team, with some high school state athletics bodies also beginning to adopt shot clocks to remove end of game stalling. Larger scoreboards include statistics on the players in the game. Basketball scoreboards must include a horn or buzzer to signal the end of a period, fouls, and substitutions; the shot clocks have their own buzzer system sounding a different octave to avert any confusion with the game clock system.