There is no "braille decoder", you have to manually decode it yourself.
Using a braille decoder.
You cannot find a Braille decoder sheet in any of the Pokemon games. Braille is very simply and easy to translate if you print off a Braille alphabet sheet for reference.
Go to wikipedia, they have a braille dictionary.
Look up a normal braille sheet on the internet
braille is a way for blind people to read. you need to get the decoder to read it.
Those symbols are braille letters. To decode them, just search "braille decoder" in google. They give you instructions on what to do to get into the next room. In the next room is one of the regis. (Regice, Regirock, Registeel)
Sadly, the game itself provides no translation sheet. However, if you take a look at one of the game's many game guides (either in print or online) there should be a decoder sheet on any source worth its salt.
To get the decoder you have to be a Secret Agent. If you are in the handbook there is the decoder which is very useful.
8:256 decoder circuit can be implemented by using 4:16 decoder circuit
The Braille Decoder sheet for unlocking the Regis in FireRed and LeafGreen was sold in the official guide released by Prima for the games. The Braille used in the games as a visual representation of the raised bumps and spaces of the braille language.
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