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 with a Q factor of 25 in the Linear Applications Handbook by National...
This circuit was found in a Japanese publication from 1971. The circuit uses components from the...
When this circuit is activated the LED flashes for a moment indicating that the function has been...