We found this circuit in a 1986 documentation. It uses only LEDs, batteries, resistors and the power supply which can consist of 4 batteries or a 9V battery. The basic circuit uses two-color LEDs.
This basic configuration of an astable multivibrator was found in a publication of the year 1968....
This simple circuit was found in an English magazine that no longer exists, January 1970 issue. This...
The circuit shown uses the 741 operational amplifier, but lower noise and higher gain equivalents...