MULTIPLEXER (MUX)

When to Use

Signal routing, data bus selection, programmable circuits, ALU input selection, display multiplexing.

Materials

• ▸2+ Redstone Repeaters
• ▸AND gate components
• ▸OR gate components
• ▸NOT gate components

Overview: what the Multiplexer (MUX) is and does

Selects one of several input signals and routes it to a single output, based on a select signal. A 2-to-1 MUX has 2 data inputs and 1 select line. Essential for bus routing.

As a logic circuit it routes, counts, or decodes signals, forming the building blocks that scale up into redstone computers.

In practice it is used for signal routing, data bus selection, programmable circuits, ALU input selection, display multiplexing. The build below targets vanilla Java Edition 1.21.

How it works: the redstone mechanics

A 2-to-1 MUX gates input A with the select signal S and input B with NOT S, then ORs the two together, so the output equals A when S is on and B when S is off. Stacking MUX stages builds 4-to-1, 8-to-1, and wider selectors for data buses.

It is assembled from 2+ Redstone Repeaters, AND gate components, OR gate components, and NOT gate components, and each of those parts plays a specific timing or logic role in the circuit rather than being interchangeable filler.

Because this is a logic circuit, the thing to watch as you build is signal isolation between stages, so one part of the logic does not back-feed into another.

How to build it

1. 1For a 2-to-1 MUX: create a select signal S and its inverse NOT S.
2. 2AND input A with S (A passes when S is ON).
3. 3AND input B with NOT S (B passes when S is OFF).
4. 4OR the two AND outputs together to get the final output.
5. 5When S=1, output=A. When S=0, output=B.
6. 6Chain MUXes for more inputs (4-to-1, 8-to-1, etc.).
7. 7Power it up and watch one full cycle: confirm it drives the correct output for each input combination before wiring it into a larger contraption.

Uses & applications

• ▸Signal routing, data bus selection, programmable circuits, ALU input selection, display multiplexing.
• ▸2-to-1 MUX (basic, 1 select line) — a variant suited to particular space or timing needs.
• ▸4-to-1 MUX (2 select lines, 4 data inputs) — a variant suited to particular space or timing needs.
• ▸Analog MUX (routes signal strength values using comparators) — a variant suited to particular space or timing needs.
• ▸Piston-based MUX (physically connects/disconnects signal paths) — a variant suited to particular space or timing needs.

Tips & common mistakes

• !Generate NOT S from the same S source rather than a separate switch, or the two select halves can briefly overlap and leak both inputs.
• !Build and verify each logic stage on its own before connecting them; debugging a full multi-stage circuit at once is far harder.
• !Remember that bare redstone dust loses 1 signal strength per block, so insert a repeater before any run exceeds 15 blocks inside this circuit.

Multiplexer (MUX) FAQ