Found in documentation from the 90s, this circuit triggers a relay with inductive signals applied to a link. The sensitivity depends on the frequency and the power supply depends on the relay used.
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...