Factorio Forums

Hello,

I'm new to this game, and I've been playing it completely without any guides, tutorials, or spoilers in general. I want to experience the game that way.

Currently I'm testing/playing with the circuit network. So, when I thought I had figured out the Decider combinator, I realized I actually hadn't.

The problem that occurs is output signals; the setup photo is in the attachment. The input of the decider combinator is a box where I store solid fuel/sulfur directly from a chemical plant, and its output is the chemical plant. You can see that the first signal is sulfur, and when I click "Set recipe" in the chemical plant, it starts to produce solid fuel (I thought it should produce sulfur). When the solid fuel becomes the first signal, it still continues to produce it.

So basically, my question is, what is the first valid recipe signal, or the first valid item signal, or the first valid entity signal as described in "Set recipe" in the chemical plant?

PS - the Switch 2 version with Joy-Cons is great (especially on TV); 101% recommend

First signal is the signal with the lowest signal ID, you have no control over it in this setup. The setup as is has no actual purpose, the condition will always be true and the outputs will always be the inputs so this is essentially just a fancy wire. You said you did not want a guide, so I am unsure if you want to know anything further.

You may want to take a look at the selector combinator, which gives you some options for sorting signals.

pn90 wrote: Thu Jan 15, 2026 8:23 am what is the first valid recipe signal, or the first valid item signal, or the first valid entity signal

Signals have an internal sorting order. If you open the signal picker dialog, signals more to the left, more to the top have higher priority, and if they're on different tabs, signals on tabs more to the left have higher priority. So the highest priority ("first signal") is the wooden chest, and the last one is the "WUBE logo (space platform)" on the bottom last tab.

A recipe signal is a signal representing a recipe but no item. For example there is a "basic oil processing" signal. This is a recipe signal.
An item signal is a signal representing some physical item that's not an entity, for example iron plate as well as water or light oil.
An entity signal is a signal representing some physical entity. That's something that can be built on the map such as a furnace or an assembling machine.

An item or entity signal can be seen as recipe: craft this item. An item signal will use the default recipe for crafting this item. If there is also a recipe signal for crafting the same item, this overrides the item and specifies which recipe to use to craft, because all recipes are more to the left/top than the corresponding items they craft.
The ordering of the types in the popup text in your screenshot is not relevant, it's just a text to explain what can be used to set a recipe in general. What matters is the ordering within the item picker.

Solid fuel is an example for this, it has 3 different recipes and 1 item signal. If you send a solid fuel signal, the chemical plant will use the "Solid fuel from petroleum gas" recipe. If you additionally send the "solid fuel from light oil" recipe, it will use the "solid fuel from light oil" recipe, because a valid recipe signal has precedence over the item signal (more to the left). If you continue to send the "solid fuel from light oil" recipe and instead of the solid fuel item signal you additionally send the "solid fuel from petroleum gas" recipe, the plant will use the "solid fuel from petroleum gas" recipe, because both are recipes and the petroleum gas recipe has precedence over the light oil one (more to the left in the signal picker).

There are also items without default recipe, although a machine could do something with it, for example the fluid barrels. If you send the water barrel item to an assembling machine, no recipe is being set. The assembling machine will not decide if it should use the fill barrel or empty barrel recipe.

Even if you don't want to consult guides, I recommend you consult the wiki if something isn't clear from the game alone and you're not able to figure it out from trial & error within the game. You can search for ingame items and skip everything else that might be a spoiler, and there are useful articles about the game mechanics. If you want to know more and are unable to figure it out from the game, this is the place where you find more information.