TIME CONTROL: While looking for chess clocks it is important to know the different types of "time control" methods available, so you purchase the chess clock that mostly meets your needs. The most commonly used time control methods are:

• Sudden Death: Chess players are required to complete a number of moves before their time is up otherwise they lose the game. For example, a player may have to complete 40 moves in 2 hours, otherwise he is eliminated.
  
• Blitz Chess: Also known as speed chess, is a variant of “Sudden Death” in which players are given a total of 5 minutes to play the game. Speed Chess or Blitz is very commonly used in an informal setting like a cafe or a public place.
  
• Fischer Increment: Invented by Bobby Fischer, is a system where by a player is given a bonus time X at the start of his turn. Obviously, if he moves before the incremented time, he would've accumulated the difference for his next move.
  
• Bronstein Delay: By David Bronstein, is a system where before the clock starts ticking, there is a short delay. If a player moves during the delay, he would've left his time intact. Otherwise, his time would've shrink by the amount used.
  

Most Analog Chess Clocks use Blitz. A tiny flag on each clock falls indicating time is up. Analog chess clocks are less accurate but are very popular among cafe chess players. Digital chess clocks offer different time control methods, they are most accurate, and are mostly used in competition. Digital chess clocks offer "time control" features more ideal for serious chess tournaments.