This amplifier was found in a tube equipment manual from 1947. The high-fidelity circuit has pentode tubes at the output and a source with transformer.
This charger for small batteries was obtained from the 1982 Radio Experimenter Handbook. The...
This shield can be used both to interface microcontroller circuits or TTTL. The resistor in series...
This circuit not only indicates when the battery is on but also when it is low. The circuit is...