Minecraft wiki entry for Clock, associated text: The basic torch pulser is the oldest clock circuit in Minecraft, simply an odd number of inverters (NOT gates) joined in a loop. The design has been mostly replaced by repeaters, but still works. Design A shows a 5-clock, which is the shortest clock that can easily be made this way. Its pulse length can be extended by adding pairs of torches and/or repeaters. Repeaters can be added into the loop, or can replace any pair of inverters. Adding repeaters also allows even-numbered clocks such as a 10-clock. The total interval is "NOT gate count" + "repeater total delay".