Emergency Flasher
A commercial emergency flasher uses a 9V battery to flash a neon lamp at approximately 2 Hz. The battery voltage is stepped up internally to provide the 600 Volts needed to flash the tube.
Unscrew the yellow cover to show the flash bulb to the class. Touch the 9V battery to the contacts to get it flashing.
See also Relaxation Oscillator (5F30.60).