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.
We found this configuration in a 1974 technical documentation. It can test both TTL logic circuits and...
This circuit emits an alert sound (interval beeps) if the car lights are left on and the ignition key...
This is an amplifier that uses a pickup coil placed next to the telephone set and the listening is done in...