A gate that does "nothing" — on purpose, and usefully. A plain-English guide to logic gates from TorchAnvil.
A BUFFER has one input and one output, and the output is a copy of the input. High in, high out. Low in, low out. Logically it does nothing at all — and it is still one of the most-placed components in any large build.
| A | Y |
|---|---|
| 0 | 0 |
| 1 | 1 |
That's the identity function. If you judged gates only by their truth tables you would delete this one immediately, which is precisely why it's worth understanding: a buffer's value has nothing to do with its logic.
A buffer exists for three reasons, none of them logical.
Delay. A gate takes time. Putting a buffer in a path pushes that signal later, which is how you line up two signals that need to arrive together. In synchronous designs this is called balancing the path, and getting it wrong produces glitches that are miserable to debug.
Signal restoration. In real electronics a signal degrades as it fans out to many inputs. A buffer reads the weak signal and drives a fresh, full-strength copy. In Minecraft the same problem appears as redstone dust losing one unit of strength per block.
Isolation. A buffer's output doesn't feed back into whatever drives its input. Dropping one between two subsystems keeps them from interfering.
Build an XOR out of ANDs, ORs and NOTs, and you'll find one input reaches the final gate through two inverters while the other arrives directly. For a moment — one gate delay — the final gate sees a combination that should never exist, and the output flickers. This is a glitch, or a race condition.
Now put a buffer in the short path. Both signals arrive together and the flicker disappears. You haven't changed the logic by a single row of the truth table; you've changed when things happen.
This is the reason a component that computes nothing has survived in every logic family ever designed.
A wire is instant and passive. A buffer takes time, and it actively regenerates the signal.
In TorchAnvil's boolean model the difference is mostly conceptual, because the simulator settles instantly. In redstone it's concrete and unavoidable: dust fades over distance, and a repeater — Minecraft's buffer — restores it to full strength while adding a configurable delay.
The repeater is the buffer, and it does all three jobs at once. It restores signal strength to 15, it delays by 1 to 4 ticks depending on how you set it, and it enforces direction — power flows through it one way only, which is exactly the isolation property described above.
There's also the Delayer in this simulator's palette, modelled directly on the repeater, with the same 1–4 tick selection.
Two redstone torches in series also make a buffer: invert, then invert back, for two ticks of delay. Builders reach for that when they want the delay without a repeater's directionality.
Redstone makes the buffer's second job impossible to ignore, because you can count it.
A redstone torch or block outputs strength 15. Every block of dust the signal crosses costs one unit. So:
| Blocks travelled | Strength |
|---|---|
| 0 | 15 |
| 5 | 10 |
| 10 | 5 |
| 14 | 1 |
| 15 | 0 — dead |
Fifteen blocks is the hard limit. At sixteen the line is simply off, and the failure is silent: no error, no warning, just a lamp that never lights and a build that works fine on the test bench and fails once you space it out.
Drop a repeater anywhere in that run and the count resets to 15. Two repeaters get you 45 blocks, three get you 60. This is the single most common cause of "my circuit worked yesterday" in large builds, and the fix is always the same: buffer the long runs.
Note what the repeater is not doing. It isn't changing a single value in any truth table. The logic was always correct; the signal just couldn't reach the far end. That's the distinction this whole page is about.
NOT(NOT A) = A(A NAND A) NAND (A NAND A)A · A = A,
and A + A = AThat last pair are the idempotent laws, and they're a neat way to see that a gate fed its own signal twice does nothing but pass it along.
The other reason buffers exist is fan-out — how many inputs one output can drive before it sags. In real logic families this is a hard number, often around ten; exceed it and every downstream gate sees a marginal voltage and starts behaving unpredictably.
Redstone has the same problem in a friendlier form. One dust line can feed several destinations, but each branch still fades with distance, so a signal split five ways and run twenty blocks arrives nowhere. The fix is the same as in silicon: buffer close to the source, then fan out from the buffer.
The demo on the right is a lever, a buffer, and a lamp. The lamp follows the lever exactly, which is the least dramatic demo on this site.
The interesting experiment is the Delayer: drop one in, set it to 4 ticks, and drive a lamp through it while a second lamp reads the lever directly. Now you can see the difference between a wire and a buffer.