Redstone circuits/Transmission

To "repeat" a signal means to boost it back up to full strength. When redstone signals are transmitted through redstone dust, their signal strength fades and must be repeated after 15 blocks. Repeater components and circuits keep signals going over long distances.

Basic repeaters
Some redstone components can repeat signals.


 * Redstone Repeater


 * The common method of repeating a signal is to use a redstone repeater. Using a block before and after the repeater, this method of repeating a signal averages 18 redstone used per 18 blocks (15 redstone dust, and 3 redstone per repeater) and 1 tick delay per 18 blocks.


 * Torch Repeater


 * When crossing long distances, redstone torches can also be used, simply allowing the signal to be inverted an even number of times during its journey. Torch repeaters use slightly less redstone than redstone repeaters (16 redstone per 17 blocks) but are slightly slower (1 tick delay per 17 blocks).

Instant repeaters
An instant repeater is a circuit which repeats a redstone signal change with no delay. A sequence of instant repeaters and redstone dust lines is known as instawire (or "instant wire").


 * Insta-Drop Instant Repeater


 * 1&times;4&times;2 (8 block volume), 1-wide
 * circuit delay: none
 * This circuit is small and relatively resource-efficient, but it depends on some unintuitive piston behavior which might be changed in future releases.
 * Behavior (Rising-Edge): While the input is off, the block of redstone keeps the lower sticky piston activated by connectivity. When the input turns on, the upper sticky piston begins to extend the block of redstone. The instant the block of redstone starts moving, the lower sticky piston deactivates and begins to retract block A, the reason the upper piston is extending -- this turns the upper sticky piston's extension into a 0-tick extension/retraction (the "insta-drop": the sticky piston "drops" its grip on the block and leaves it behind when it retracts), leaving the block of redstone above the lower sticky piston and powering the output. All of this happens instantly (in the same redstone tick), effectively allowing a rising edge to pass through the circuit with no delay. Now that the block of redstone is above the lower sticky piston, the lower sticky piston extends again, and two ticks later block A is back in position causing the upper sticky piston to extend again, ready to retract block A when the signal turns off.
 * Behavior (Falling-Edge): When the input turns off, the upper sticky piston begins to retract the block of redstone, immediately cutting off power to the output, effectively allowing the falling edge to pass through the circuit with no delay. While the block of redstone is moving, the lower sticky piston deactivates, but then activates again when the block of redstone stops moving and can activate the lower sticky piston by connectivity again.
 * Earliest Known Publication: February 14, 2013.


 * Dust-Cut Instant Repeater


 * 1&times;6&times;4 (24 block volume), 1-wide
 * circuit delay: none
 * This circuit is a little larger than the Insta-Drop Instant Repeater, but it uses mechanics which are well understood and likely to remain intact in the game.
 * Behavior (Rising-Edge): When the input turns on, the lower sticky piston begins to extend, causing the upper sticky piston to retract, allowing the powered redstone dust below block A to connect to the output. All of this happens instantly (in the same redstone tick), effectively allowing a rising edge to pass through the circuit with no delay. The input signal also turns off the redstone torch which is the power source for the redstone dust, but it takes 4 ticks (1 tick for the redstone torch, and 3 ticks for the repeater) before that would turn the dust off and by that time the block of redstone has been extended and can continue powering the redstone dust.
 * Behavior (Falling-Edge): When the input turns off, the lower sticky piston begins retracting the block of redstone, immediately cutting off power to the output, effectively allowing the falling edge to pass through the circuit with no delay. The input turning off also allows the redstone torch to turn back on, but by the time it powers the redstone dust, block A has cut the output line.
 * Variation (2-Wide): The two upper levels (including the dust on top of the block the repeater is facing) can be moved one block over and down, and the last block on the lower level and its dust removed, to make a 2-wide version which is shorter in height and length (but larger in volume: 2&times;5&times;3, 30 block volume). In this version, to reduce the amount of redstone used, the block of redstone can be replaced with a regular block if redstone torches are placed under both its extended and retracted position.
 * Earliest Known Publication: January 3, 2013.

Two-way repeaters
A two-way repeater (a.k.a. "bi-directional repeater") is a circuit which can repeat a signal in either direction.

Two-way repeaters have two inputs that also act as outputs.

Typically the problem to be solved in design is repeating the signal in either direction without repeating the signal back into the same input which could create a clock or a permanently-powered repeater loop.

Current designs also have a reset time -- when input from one side is turned on, and then input from the other side is also turned on, then the first input turned off, there is a short time while the transmission on the first side remains off until the circuit can reset itself to allow the second input through. Thus, the reset time can be seen as a spurious off pulse in a line that should be on.


 * Repeater-Lock Two-Way Repeater


 * 3&times;4&times;2 (24 block volume), flat, silent
 * circuit delay: 1 tick, reset time: 3 ticks
 * When a signal comes in from either side, it blocks the other input with a repeater lock.
 * Variation (Offset Input): The circuit shown in the schematic to the right keeps the transmission lines in-line with each other, but reduces the signal strength by 1 in side movement in both input and output before continuing the transmission, so the circuits must be placed with only 11 dust between them to work. Placing a block behind each of the input repeaters and moving the input/output lines closer to the repeaters' outputs means that signal strength is only lost in side movement at input, allowing an additional dust between the circuits (and thus a more efficient transmission), but requires that the transmission lines alternate which side they run on.
 * Earliest Known Publication: December 21, 2012


 * Comparison Two-Way Repeater


 * 2&times;5&times;2 (20 block volume), flat, silent
 * circuit delay: 2 ticks, reset time: 4 ticks
 * When a signal comes in from either side, it blocks the other input by providing a strength 15 signal to its comparator's side.
 * It's possible to override or block this circuit with additional inputs from the comparators' other sides.
 * Variations: Opaque blocks can be placed before and after the repeaters to increase the length of the circuit (as the usual point of a repeater is to cross distance efficiently).
 * Earliest Known Publication: February 16, 2013


 * CubeHamster's Two-Way Repeater


 * 2&times;6&times;3 (36 block volume), silent
 * circuit delay: 2 ticks, reset time: 3 ticks
 * The output on each side is produced by the redstone torch under the block, held unpowered by the input torch from the other side. When the other input signal turns on, the output torch turns on -- this also turns off the input torch holding the other output torch off, but each output torch also holds the other output torch off, keeping the circuit from becoming permanently powered.
 * Variations: If it's not necessary to get the signal back to the lowest level (such as if this is built in a 1-deep hole), then this circuit can be considered to be 2&times;4&times;3 (24 block volume) and thus only four blocks long.
 * Earliest Known Publication: August 9, 2012


 * Original Two-Way Repeater


 * 3&times;4&times;3 (36 block volume), silent
 * circuit delay: 2 ticks, reset time: 4 ticks
 * This design offers few advantages over the other designs, but may be appropriate for some needs.