This circuit divides the grid 60 Hz frequency to obtain 20 Hz to drive mechanical watches used at the time. The circuit is from a 1970 CQ magazine.
This circuit was published in an English magazine from 1980. The magazine no longer exists, but...
We found this circuit in an old American documentation, from 1971, but the component used is still...
This circuit is from a 1991 publication, but it can be assembled with more modern components. We...