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.
This circuit was found in a General Electric / RCA documentation from the 1980s. The circuit is...
We have in the diagram another way to make the null adjustment of an operational amplifier. In...
The presented circuit was developed to control a common remote-control servo. Its operation is...