Found in an English publication in 1969, this circuit has a 600 kHz pass band. Ferranti's transistors support modern equivalents.
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...