Minecraft wiki entry for Pulse, associated text: The circuit will produce four 1-tick pulses for every item placed in the middle hopper (with a 1-tick off-pulse between each on-pulse). The total number of pulses may be reduced by 1 by changing the 4-tick repeater to 2 ticks, or reduced by 2 by replacing the 4-tick repeater with a block, or increased by 1 by changing the 1-tick repeater to 3 ticks.