This simple circuit is a continuity test that, in addition to testing resistors, can also test other components. Power is provided by batteries and the LED can be of any color.
We found this simple alarm circuit in a 1986 documentation. The circuit uses sensors of the NA...
This sound relay or Vox was found in 70s RCA documentation. SCRs can be common types today and...
Placed near a common receiver, this oscillator is intended to generate a beating signal to receive...