Flood alarm (CB7994E)

This circuit is from a 90s Popular Electronics. The transistors are of general use and the buzzer is a Sonalert type.

JFET Current Drain (CB13422E)
This circuit was obtained in a 1974 documentation. It shows how to use a JFET as a low intensity...
Schmitt Trigger (MSB020E)
Schmitt Triggers convert a signal of any waveshape in square signals or pulses. The circuit shown...
Ultraviolet Radiation Meter (CB12215E)
This circuit was found in a 1992 publication. The critical component is the photodiode, but...