Brief principle of operation:
1. The generator creates pulses of about 10 Hz and transmits them to the coil.
2. The magnetic ball rotates in the coil from the pulses and creates an electromagnetic induction in the coil and feedback occurs with the generator.
3. With a slight increase in the frequency of the generator, the rotation of the ball increases greatly and creates a resonant frequency of about several kilohertz.
Circuit operation emulator (without magnet) - http://tinyurl.com/y2g5f58u
Magnet balls 5MM - https://aliexpress.com/item/20-5-DIY-...
Schematic diagram of the generator - http://anod7.ru/files/crazy-ball.png