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.
Found in American documentation from the 90s, this circuit provides three timings given by the...
This circuit is basically the same configuration as the previous one with a power stage with...
This dual-operator thermometer circuit was found in the September 1982 issue of Radio Electronics...