Redstone Repeater

A redstone repeater is a block used in redstone circuits to "repeat" redstone signals back to full strength, delay signals by 1-4 redstone ticks, prevent signals moving backwards, or to "lock" signals in one state.

Jungle Temple
A single redstone repeater can be looted from each naturally-generated jungle temple.

Usage
A redstone repeater has a front and back – the arrow on the top points to the repeater's front. A repeater also has two small redstone torches on its top – the color of the torches indicates whether its output is on (dark red when off, bright red when on) and the distance between them indicates the delay the repeater adds to the signal transmission.

A repeater can only be placed on opaque blocks (dirt, stone, etc., but not glass, leaves, etc.), or upside-down slabs or stairs. If the support block is moved or removed, the repeater will turn back into an item as if "mined".

A repeater is 0.125 blocks high (1/8 of a block).

Signal transmission
A repeater only transmits signals from its back to its front, but its behavior can be modified from the side (see signal locking, below).

A redstone repeater can be powered by any of the following components at its back:
 * an active power component (redstone torch, lever, block of redstone, etc.)
 * powered redstone dust
 * a powered redstone comparator or another powered redstone repeater facing the repeater
 * a powered opaque block (including any opaque mechanism component such as a dispenser, redstone lamp, etc.)

A redstone repeater can power any of the following components at its front:
 * redstone dust
 * a redstone comparator or another redstone repeater facing away from the repeater
 * a mechanism component (such as pistons, doors, etc.)
 * an opaque block

An opaque block powered by a redstone repeater is called "strongly-powered" (as opposed to an opaque block "weakly-powered" by redstone dust). A strongly-powered opaque block can power adjacent redstone dust, as well as other redstone components.

Signal repeating
A redstone repeater can "repeat" a redstone signal, boosting it back up to power level 15.

Redstone signals have a maximum power level of 15 and that level drops by 1 for every block of redstone dust the signal travels through. If a signal must travel through more than 15 blocks of redstone dust, a redstone repeater can be used to boost the signal back up to full strength. An extra two blocks of distance can be achieved by placing solid opaque blocks before and after the repeater.

While redstone repeaters can allow signals to travel great distances, each adds some delay to the transmission. An alternative is an instant repeater circuit (aka Instawire) which allows distance transmission with no delay.

Signal delay
When initially placed, a redstone repeater has a delay of 1 redstone tick (equivalent to 2 game ticks, or 0.1 seconds).

By right-clicking on the repeater, a repeater's delay can be set from 1 to 4 ticks (indicated by the distance between the two small redstone torches on the top of the repeater). Longer delays can be made with multiple repeaters – for example, a repeater set to '4' and another to '1' will give a half second delay (0.4s + 0.1s = 0.5s).

A repeater set to a delay of 2-4 ticks will increase the length of any shorter pulse to match the length of the repeater's delay. For example, a repeater set to a 4-tick delay will change any shorter pulse into a 4-tick pulse.

Signal direction
A redstone repeater acts as a "diode" – it will only allow redstone signals through in one direction (unlike redstone dust or opaque blocks which can transmit redstone signals in any direction).

A diode can be used to protect a redstone circuit from redstone signals feeding back into the circuit from its output, or can be used to isolate one part of a circuit from another.

Alternative diodes include redstone comparators and transparent diodes.

Signal locking


A redstone repeater can be "locked" by another powered redstone repeater facing its side. When locked, the repeater will not change its output (whether powered or unpowered), no matter what the input does. When the side repeater turns back off, the repeater will go back to its normal behavior.

A repeater can also be locked by a powered redstone comparator facing its side. This offers additional possibilities for locking signals because a comparator's output can be affected from 3 sides as well as by containers.

While a repeater is locked by another repeater (but not by a comparator), the small movable redstone torch on top will change into a bedrock bar, indicating its locked status.

Trivia

 * In the coding, the redstone repeater is referenced as "diode".
 * If the player shoots an arrow onto a repeater, every time the repeater changes state it will make the sound that arrows make as they make contact with a block.
 * Snow tiles are exactly the same height as repeaters.