Same as D+55+12 using speaker for audio tone generation.

Same as D+55+12 using speaker for audio tone generation. 90 Volts D.C. is put across a series RC circuit. A neon bulb is in parallel with the capacitor. When the capacitor charges up to 80 volts, the neon bulb flashes (breakdown voltage for this neon bulb is about 80 volts), draining the capacitor charge. The capacitor then begins to charge again, and the cycle repeats. The period T of the flashes of the bulb is the product of the Resistance and Capacitance (RxC). The resistance can be varied from 0 to 5.5 M ohms, and three different capacitors can be plugged in: 2 micro f, .47 micro f, and .01 micro f. The oscillating signal produced in this demo is amplified and made audible with a speaker.The signal frequency f = 1/T.