Triple Block time control

The Triple Block time control, abbreviated TB and also called TriBi or Tri-Bi, is used in correspondence chess, where moves are transmitted over distance and a turn may last for days. It is a system of the International Correspondence Chess Federation, abbreviated ICCF. Instead of placing all available time in one counter, it divides that time among three blocks with different functions.

The three blocks

• Clock: time immediately available for the current move. It begins at 50 days and can never hold more than that.
• Increment: time released automatically after each move during the first 50 moves.
• Bank: reserve time that can be transferred to the clock to restore working room.

After a move, the system refills the clock from the increment and, where applicable, the bank, without exceeding the 50-day maximum. While it is the player's turn, time can also be moved manually from the bank. The exact increment, bank, and overall event duration depend on the event configuration.

The critical rule is that the active clock must not reach zero. If it does, the player loses on time even when the bank still contains time or future increments remain unearned. The system measures reflection time in days, hours, minutes, and seconds, and replaces separate leave with freedom to manage the available reserve.