Simple brake light


I’m looking to make the simpliest way to get a “on/off” brake light (by pressing remote trigger). thinking of this: on brake, get ppm signal from Receiver (GT2B) and light on LED (powered by an ubec 12s to 12v) . I’m thinking of making this with relay, but how to only get “brake” signal and not “accel” signal ?

After reading lot of topics on lights system I can’t find solution without some arduino (or attiny85) solutions.

It seems that parts like this: are working , but for 5v