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.
The integrated circuit used in this amplifier is not common today. The power can be between 4 and...
This circuit was obtained from a 1997 publication. It is an alarm that has a lock and a bistable...
We found this circuit in a 1991 publication. What it does is to amplify a signal with unit gain...