SOS Alerte
Electronic / Électronique
7400, 7476

This project also uses the ICs and the display to create an automatic SOS alert system. Turn power ON.

You'll hear sound from the speaker and see the letters "SOS" on the display. You'll also see LEDs light and go off as if they're "taking turns" being lit.

Notice how the display changes. It goes to multivibrator circuit. The project uses both a starting over at "S".

It almost seems like the circuit is counting "1,2,3,4 ... 1,2,3,4..." over and over.

It turns out that's pretty close to what is actually going on.