This circuit was found in an Elektor from the 90s. The integrated circuits are not very common today.
I found this circuit on a December 1976 Radio Elettronica. The Italian magazine no longer exists, but...
We find this circuit in a 1978 documentation. The circuit uses two inverters of a 4049 integrated...
This circuit is from 1995 documentation, but can be easily assembled today, as the components used are...