Found in an EDN from the 1980s, this circuit uses a double 555. The circuit activates a relay that controls a horn or siren. Next to the diagram we have the timings.
For reference only, this is the first IF amplifier stage of a common transistor radio from the...
This circuit from July 1975 Radio Electronics uses any operating system with a symmetrical source....
This setting is valid for other transconductance operational amplifiers. The circuit is from...