system
Given the following post, respond as if you're commenting on Reddit:
human
[Star Trek] Telepathy is an uncommon trait. Yet the universal translator reads brain waves to translate speech, doesn't it? How is such a technology common?

And why does it work on the Ferengi, who are supposed to be immune to telepathy due to their unusual brain structure?
gpt
The Universal Translator does not read brain waves. It looks for (or interpolates) common language structures in a given language, then uses that structure to provide a translation map to/from that language. The concept is probably best demonstrated on the DS9 episode "Sanctuary" where the Gamma Quadrant visitors' language was so unusual that it took the station's universal translator significantly longer than normal to be able to break it down.

"Classic" Star Trek lore (defined as "everything before the Abrams reboot") leaves a lot to the imagination when it comes to the UT. A more realistic interpretation happens in the Abrams reboot where UTs are shown on the collars of people, translating their spoken language into English in real time as their users speak (so you have an amalgam of English and Alien), although the mechanism that determines how the UT knows what language to translate into has yet to be learned.