Darkness Monitor (CB21019E)

Found in Popular Electronics this circuit triggers an SCR and lights an LED when the location of the sensor is dark.

| Clique na imagem para ampliar |

Simple Relay Shield (CB21223E)
This circuit was found in old American documentation. Transistor is general purpose and relay is...
Simple Alarm (CB25944E)
This simple alarm with latching uses a relay as the main element. The circuit is from a Radio...
Telephone Pickup (CB12308E)
This circuit is from an Italian publication called Fare Elettronica from 1987. What we have is an...