For me that is blue leds.
replyYes! I remember thinking "damn you band gap physics, if we only had blue leds we could do colour displays with LEDs, but that can never happen."
reply"rareleds" on Instagram is fantastic. Vintage LEDs set to apex twin and so on
replyI also remember being amazed, and did a forehead slap, when an old army bomb disposal man explained how, what I thought was an innocent device, was used by the IRA in bombs.
replyHa. When I was a teenager I used to build 555s into timers for the same purpose using a no PCB rats nest construction.
replyThough surprising the family at dinner with a small explosion was a much more innocent purpose.