This circuit is from an old Japanese publication of 1962. The circuit uses two batteries, one for the filaments of the tubes and the other one of high voltage for the plate circuits.
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...