Light test (CB8789E)

This light-sensing probe was found in a 90s Popular Electronics. The circuit detects light sources by triggering a buzzer.

Simple ohmmeter (CB23622E)
Combined with the two previous circuits, we can create a simple multimeter with this circuit. The...
Amplifier for instrument (CB21328E)
This 1.5V instrumentation amplifier was found in National Semiconductor documentation from the...
Bulb Saver (CB16631E)
This simple circuit helps to save incandescent lamps by leaving their filament slightly heated and thus...