This circuit was found in documentation from the 90s. The operational amplifier is NE5514, which is uncommon today. The configuration can be adapted to use modern components.
This circuit was obtained from a 1978 Practical Wireless. It causes an LED to flash at a frequency that...
We found this circuit in a 1986 publication. However, as it is based entirely on 555 integrated...
This circuit with an integrated circuit of the time was found in the magazine Radio Electronics of April...