This alarm with automatic shutoff was found in the April 1975 Radio Electronics magazine. The activation time is given by C1 and R3. The alarm uses series and parallel sensors.
We found this circuit in a Popular Electronics of the 90s. The circuit still uses light bulbs, but...
This circuit is from Linear Technology 2005 documentation. The circuit is based on company...
The integrated circuit used in this power supply is no longer very common in power supplies today....