Based on a 555, this 80's American documentation circuit detects the voltage of a battery and can then disconnect the charger. The transistor may be a general purpose type.
This circuit was obtained from an American 1980s documentation. The frequency depends on the...
This circuit was found in an American documentation. Its purpose is to allow the use of a digital...
The sensor diode used in this circuit is the common type of germanium. Experiments may be made...