This high sensitivity circuit was found in the July 1992 Radio Electronics magazine. The circuit drives a buzzer, but a relay can be used to activate an external load.
This circuit is from a 1991 PE Hobbyst Handbook. The circuit uses two trigger transformers for a xenon...
A JFET is used in this circuit to maintain constant gain. The circuit is from an Electronics Now...
Found in a Popular Electronics from the 90s, this circuit uses a double 555 to emit beeps when the...