This circuit was suggested by National Semiconductor and is present elsewhere on this site. The LM2575 is not very common today and should be mounted on a heatsink.
This circuit can be connected to the output of alarms or sirens with the 555, CMOS or TTL,...
Found in an American leaflet from the 90s, this circuit uses an AM radio out of station to monitor...
Found in the Encyclopedia of Electronic Circuits Volume 5 of 1995 this circuit has the gain...