Found in 1968 Mullard documentation, this circuit uses period components. The transistors are matched pairs and the sensor is an Indian photocell of the time.
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...