Filament source (T398E)

Despite being transistorized, this is a constant current source circuit for 1 V valve filaments such as the 1H4 tube.

Digital Potentiometer (CB12805E)
The resistance found between the R terminals of this circuit depends on the digital programming made at...
2 transistor radio (CB20517E)
This circuit with germanium transistors was found in documentation from the 50's. The transistors are...
Battery charger with current and voltage limiter (CB9537E)
This battery charger circuit was found in ancient American documentation. The components are...