a strobe tuner was the 1st type of electronic tuner, manufactured in the 60's & 70's. It transferred the signal of the guitar into a radio wave, you adjusted the tuning until the wave flatlined. They were big, bulky, and a pain in the ****, one of my old guitar teachers used to have one that he made me tune to every lesson, I hated it. Alot of techs swear by them though.