Redstone Comparator

The comparator is a block for use with redstone circuitry. It has two inputs: one from the back ('signal A') and one from the side ('signal B'). If signal B is stronger than signal A, there will be no output. Otherwise, it can be set to either repeat signal A at its current strength, or output the difference between both inputs.

It also provides a "subtraction" feature which results in the output being the strength of the back ('signal A') being subtracted by the side ('signal B'), however for this to work the player must make sure that the front redstone torch is lit and also use another comparator into the side for it to work. Signal B has to be less powerful than signal A for it to work. Right-clicking the comparator will toggle the torch. The torch must be on for comporator subtraction to work.

The comparator looks similar to a repeater, except with an additional redstone torch.

Trivia

 * It takes 0 ticks for the comparator to change state.
 * The comparator does not, however, re-strengthen a redstone signal. This means it can not be used for Super long instant circuits. It does, however, enable instant gates.

Gallery
Komparator Comparador de Redstone Comparateur Компаратор 红石比较器