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.
This VCO or Voltage Controlled Oscillator uses common components. TR1 can be a BF245 and TR2 a...
The transformer for this project found in a 1986 documentation is an output type, found on old...
We found this circuit in a 1978 documentation. The SCR conducts when the regulator's output...