The transistor used in this circuit is uncommon today. AC124 or equivalent such as AC188K and 2N2431 can be used. The circuit is from the 80's and makes use of transformers.
In the figure we have a typical relaxation oscillator with a SIDAC as well as waveforms and...
This ultra-simple circuit need a carbon microphone to operate. The circuit must be powered from D...
The galena XTAL is replaced by a germanium diode in this Project. Diodes such as the 1N60 or 1N34...