This diagram was found in the November 1972 issue of Radio Electronics magazine in an article describing benchtop equipment. The transistors are of the time and the frequencies are given by the coils.
We found this circuit on the internet. The components are current, and the time depends on C1...
This circuit was found in an English publication of 1982. The operational can be replaced by an...
With this luminous remote control, which we found in a 1990 publication, using a flashlight you...