This crystal oscillator generates a 20 MHz signal. Equivalent transistors such as BF494 and 2N2222 can be used. The stabilizing diodes can be 1N4148.
In the figure we have the way to make the three-phase control of a motor using opto-diacs. The circuit is...
This circuit for testing the voltage gain of a transistor was found in the March 1953 issue of...
This circuit was found in a PE Hobbyst Handbook from 1992. The second oscillator is a VFO. The...