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 is the receiver circuit for the previous transmitter (CB19628E). The receiver is an infrared...
This circuit was found in old American documentation. Transistor is general purpose and coil rated...
Found in English documentation, this touch sensitive switch must be powered by an isolation...