In this charger the current is limited by the incandescent lamp. Lamps from 40 to 100 W can be used and even connected in parallel, depending on the load.
This electronic Morse Key for telegraph message transmission was found in an American 1980s...
This PWM control circuit was found in an old documentation, but appears elsewhere on this site...
Found in a 90s Radio Electronics, this circuit uses an AD590 or AD592 for remote temperature...