This circuit was published in the July 1993 issue of Electronics Now magazine. It uses a sensor from the time and triggers a buzzer with a Sonalert-type oscillator.
This configuration was obtained in a 1977 FET Databook. The circuit can be practically any JFET...
The integrated circuit used in this regulator is not very common today. The circuit is from old...
The operational used is uncommon today, but equivalents can be used. Unlike the previous one, this...