Minecraft Sign as a display?

I would like to have a sign in Minecraft with something on it such as the till or something and as soon as there's a redstone signal there should be something else on the sign but it should be there as soon as there's no redstone signal again build something and if so how? It's also ok if it only works with command blocks.

Is possible. I'll explain how in a moment.

I think with a certain / set block command

But I don't know about commands, sorry

But a little tip: watch tutorials from TheJoCraft or MumboJumbo on YouTube

But then you looked for a hard chunk. I'm still trying to answer the question for you.

First of all you build your "checkout" sign somewhere where there's space. Then you stand on the same block where the sign is now. Now enter the command:

/ blockdata ~ ~ ~ {}

This will give you the NBT data for this block (here sign), which you can copy.

(If you do not get the NBT data try to stand on a block that hovers directly above the sign and change the "~ ~ ~" for "~ ~ -2 ~".

Write them down somewhere (preferably on the computer for copy-paste) and do the same again with the alternative sign.

If you now place a command block 5 blocks (or more / less) under the correct position, you can change the NBT data with the following command.

/ blockdata ~ ~ 5 ~ {NBT data}

You do that with the other NBT data too.

I have now built this but I have another problem because once this cycle is carried out there's the second one all the time and does not switch back to the till