Unlike the previous one, this circuit is intended for the reception of frequency modulated signals transmitted by the power grid. The circuit is from a Radio Electronics from February 1989.
According to the author of this project, from a documentation on espionage from the 1980s, this...
This circuit suggested by Siemens can provide time intervals for triggering values that are given...
This circuit generates a good-intensity 1 kHz rectangular signal. The circuit is from Electronics Now...