Broadband amplifier (CB9005E)

For a 75ohm output, this circuit was found in ancient American documentation, using components from the time.

Sound Operated Switch (CB6315E)
This sound relay or Vox was found in 70s RCA documentation. SCRs can be common types today and...
2 Door Announcer (CB4757E)
This two-door doorbell was found in a 1990s US publication. The circuit is still current as...
Magnetic field meter (CB7061E)
This sophisticated circuit using a liquid crystal display was found in Radio Electronics from the...