Do you know what interfacing means?
Make a note of what you think ... this Project will give you some clues. Unlike most of our earlier multivibrator circuits, this one doesn't connect to a LED or another digital circuit ... this one operates the Relay.
After you finish the wiring connections, press the Key. Listen carefully and you'll hear the Relay switch ON and OFF as the multivibrator generates pulses.
Since the Relay is a type of switch, you can control other devices by connecting them to the Relay. You might notice that there is a good bit of time between pulses.
Try substituting different values for the 22K resistor and 100µF capacitor.
Oh yes - interfacing!
Interfacing is how digital circuits work together with the outside world. This is a very simple Project, but it does show a digital circuit can be used to control various devices.
Computers are big users of interface circuits and devices — that's how we humans are able to talk with computers. Can you think of some other examples of interface circuits?
(Ask your teacher or librarian for some books on computers — you'll find examples of many interfacing devices in them.)