Power grid voltage failure indicator (CB7013E)

Found in an 80's Elektor, this circuit can use any equivalent optical coupler. The buzzer is of the Sonalert type with included oscillator.

| Clique na imagem para ampliar |

Symmetric Power Supply 15 V x 1.5 A (CB14525E)
The integrated circuit used in this 1990 project is uncommon in our market, and transistors...
Transistor as Detector (CB12235E)
The circuit shown is a suggestion given by an English publication from 1980. In it, a...
Square Triangular Generator with the LM3900 (CB13511E)
This circuit is from 1977 Radio Shack documentation. The frequency depends on the capacitor. The...