This circuit is from a 1924 book by Gernsback. The receiver uses two tubes and listens to headphones. Power is supplied by battery with the indicated voltages.
This power supply with transistor regulation was obtained in a 1995 documentation. The power...
This two-station intercom was found in documentation from 1966. R4 should be experimentally...
We found this circuit in a publication from 1966. The components are from the period. Complete...