This circuit was found in an American documentation from 1969. The circuit is a multi-indicator with resistors typically 47 k for R1 and 100 k for the others.
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...