Silent alarm (CB22471E)

This circuit is from a Popular Electronics from 1992. The circuit powers an LED when triggered.

10 A Bidirectional Current Sensor (CB5261E)
With this circuit it is possible to monitor the charge and discharge of a battery. The circuit is...
Variable High Pass Filter 23 to 700 Hz (CB25821E)
This high pass filter was found in the February 1996 Electronics Now magazine. The circuit...
Charger and Regulated Adapter Nicad (CB19075E)
This automatic nickel-cadmium or NiCad battery charger was found in European documentation from...