This circuit was found in a 1924 Gernsback publication. The variable capacitors are dual. Listening is through a high-impedance phone.
In the figure we have a negative power circuit for SCR and unijunction transistor suggested by...
We found this oscillator in a documentation for radio amateurs from the 1970s. The circuit can use...
This 5 V power supply for TTL, Shields and microcontrollers is old, and the components can be...