This circuit of starting lights for auto-race was found in an English documentation from the 80's. The LEDs must be of different colors, for greater realism.
The author of this 1995 article called it PWM, but it is really a switched source. The circuit...
Found in American documentation from the 1980s, this circuit for general purpose transistors has good...
Suggested by a Popular Electronics from the 90s, this circuit triggers an external load, relay or...