This circuit was obtained from an American 1980s documentation. The frequency depends on the crystal and the circuit may be a PNP that reaches the generated frequency.
This circuit can be used to detect the signals from the previous circuit or from any radio...
The integrated circuit used is uncommon today. The numbering in parentheses is for the second...
Using the CA3140 in the figure we have a comparator that goes low in the window voltage space. The...