This circuit was found in a Signetics documentation from the 1980s. Next to the figure are the waveforms of the generated signals. The transistor admits equivalent.
The transistor of this constant current source may be the BC548 or equivalent. Resistor R2 may be...
Based on the 4006 this circuit generates random signals in a frequency range that depends on L1...
The BFO or Beat Frequency Oscillator is used to receive telegraphic signals or even modulated in...