This sound relay or Vox was found in 70s RCA documentation. SCRs can be common types today and transistor a BC558. The circuit is for the 110V power grid.
We found this circuit for vocal effects in the September 1990 issue of Radio Electronics magazine. The...
This circuit was found in a 80’s American documentation. The adjustment trimpot is from 47k to...
This circuit produces a single pulse whose duration depends on the capacitor. The circuit is from an...