This unijunction transistor circuit is a frequency divider synchronized to 100 kHz. The circuit was found in a Radio Electronics from July 1968. The adjustment of R4 is important.
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...