Minecraft: How to make Redstone Repeater
2 Redstone Torch + 1 Redstone + 3 Stone --> Redstone Repeater
Can be used to control the flow of a Redstone signal. (Only allows signal to travel 1 way thru the repeater)
Can be used to "boost" the signal, thus extending the distance a Redstone signal can travel. (About every 16 blocks)
Can be used to send a signal thru a single block and received on a different side.