Redstone Comparator

The Comparator is a block planned to be added in the Redstone Update for use with redstone circuitry. It will have 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 increase it to full strength. Dinnerbone expresses interest in a new ore for these, stated to likely be in the Nether to promote exploration.

Trivia

 * The Comparator looks similar to a Redstone Repeater, just only a little different.
 * It takes 0 ticks from the Comparator to change state, this way you can build very fast redstone circuits