This circuit is from a Radio Electronics magazine from May 1986. Observe the voltages applied to the capacitors, taking care that the capacitor under test can withstand them.
This simple transistor tester circuit was found in the February 1968 issue of Radio Electronics magazine....
This powerful inverter provides a high-quality sine wave signal. I found it in a Radio Electronics issue...
This squelch is activated by its own noise, acting automatically. It is used in communications...