Found in a RE Experimenter Handbook from the 90s, this circuit is intended for the use of LEDs in a flashing system for Christmas trees. The circuit can be expanded
This circuit was found in a 1998 documentation but uses common components that can still be found...
This high quality circuit with complementary symmetry was found in an Electronics World of 1966....
This simulated circuit uses a 741 (Operational Amplifier), but other operational amplifiers can be...