Found in American documentation from the 1980s, this circuit has a diode feedback. At the exit we have an indicator LED. The LM3900 is a transconductance operational amplifier.
We found this circuit in a 1968 Electronics World. The potentiometer should be set to trigger the SCR...
The Variable Frequency Oscillator (VFO) or Variable Frequency Oscillator shown in the figure can...
This circuit provides a power per channel between 6 and 10 W depending on the load. The circuit is from...