This interference rejection circuit for telegraphy was found in a 1980s documentation for radio amateurs. The integrated circuits used are common today.
This circuit was obtained from an 80's Electronic Engineering. The circuit detects ice formation...
This circuit is from the Motorola Linear Databook published in 1990. The circuit for 1 kHz can be...
In the fist circuit the alarm triggers on when any sensor is CUT. In the second circuit the alarm...