For a better understanding of the buzzer’s operation, look at the circuit diagram. Imagine you’ve just pressed the code key down. Let’s see what happens, starting at the corner terminal of the battery.
Circuit Diagram
Instantly, current shoots downward to the brass contactor screw. Since the screw is touching the vibrator arm, the cur- rent continues on its way into the coil. Out of the coil it streaks past the closed code key and back to the battery.
As in the electric pencil, this flow of current creates a magnetic field around the iron bolt. Having become an electro- magnet, the bolt attracts the vibrator arm. But as the arm starts to swing toward the bolt, it opens the circuit. Hence, the current stops. As a result, the magnetic field collapses, allowing the vibrator arm to spring back against the contactor. With the circuit now restored, current starts flowing again . . .and the cycle starts anew.
No matter how quickly we press and release the code key, the current will still make hundreds of round trips through the circuit. And because of the resulting rapid motions of the vibrator arm, a buzzing sound is heard.
Not only is the code set fun to build, but it is even more fun to use, especially with a fellow operator. So that both of you can send as well as receive messages, you will want to build two identical sets of buzzers and code keys. They’re really not hard to make. For each set you will need the following materials.