Start and Stop Signals

Overview

In many sports an official controls exactly when play or a race may begin and when it must stop, using an audible or visual signal that every competitor perceives at the same moment. For races, a starter brings the field to a set position and then fires a gun, sounds a horn or gives a spoken command, and that same instant starts the clock. In team and court sports a referee's or umpire's whistle both begins play — a kick-off, a face-off, a throw-off, or the authorising of a serve — and halts it for fouls, scores or safety. A bell opens and closes rounds in combat sports, while a buzzer, siren or hooter marks that a period is over once time expires.

Because the signal is the shared reference for when action becomes legal, officials watch the starting moment closely. Moving, leaving the blocks, or breaking from the line before the signal is a false start; the start is recalled and, depending on the sport, the offender may be warned, penalised, or — in some sports — disqualified immediately. The stopping signal matters just as much: play is dead the instant it sounds, so a goal, shot or stroke completed afterwards may not count. The same official and signal also govern every restart after a stoppage, so a single authoritative source threads through the whole contest, keeping all competitors working from one clock and one shared moment from the first whistle to the final hooter.

What it involves

Common instruments vary by sport: a starter's pistol or horn for races, a referee's or umpire's whistle for team and court games, a bell for combat rounds, and a buzzer, siren or hooter to end a period or signal an expired countdown clock.
The signal exists so every competitor reacts to the same instant — it fixes when action becomes legal and, in timed races, is the exact point at which the clock starts running.
Reacting before the signal is a false start: a competitor moves, leaves the blocks, or breaks from the mark too early. The start is recalled, and depending on the sport a false start can bring anything from a warning to immediate disqualification.
When the stopping signal sounds, play is immediately dead, so a score, shot or stroke completed after it usually does not count — which is why buzzer-beating timing is judged so precisely.
The same official and signal manage every restart after a stoppage, so one authoritative source controls the rhythm of the whole contest from the first whistle to the final hooter.