Low Voltage Test (CB22158E)

This is a simple voltage tester for voltages from about 2V to about 15V with the indicated resistor and red LEDs.

CMOS 4001 Alarm with Latch (CB24374E)
We found this circuit in the April 1975 Radio Electronics magazine. The circuit has a latch and...
Alarm System (CB16793E)
We found this sophisticated home alarm in a 1994 documentation. The circuit supports sensors of...
Light Activated Alarm (CB26164E)
This circuit was found in the 1991 Electronics Experimenter's Handbook. It activates a relay when...