This circuit uses a capacitor that depends on the frequency of the crystal. We found it in a 1967 documentation. The maximum frequency is around 100 kHz.
This circuit is from an Electronics Now from August 1995. The triac is according to the load that...
Although it was found in a British magazine 1976, this circuit can be easily upgraded with the...
This circuit was found in the January 1992 issue of Radio Electronics magazine. The capacitor...