We found this circuit in the October 1991 issue of Radio Electronics magazine. The circuit uses common components and can still be assembled easily today.
Using red LEDs with ignition voltages of the order of 1.5 V we can make a multiple voltage...
The frequency range of this generator depends on C which can have values between 1 nF and 1 uF....
This circuit is from a 1972 Motorola publication. The used transistor can still be found, but it...