Morse code. Did a science project back in middle school with wires, buzzers and tappers on a board. Then I taught it to my boy scout troop for a badge. Then lost some of it before joining the army in communications (as well as a ton of other outdated means of communication) and then in Iraq, me and another commo guy wired up our rooms for it so we could talk shit about our leadership even if they were in the room. Anyways, after working with it that many times over a stretched out time frame, I’ll never forget that. Or the phonetic alphabet.