The sound signaling the beginning and end of classes is indispensable to every school. Nowadays, this job is mostly done by an automatic bell system which plays tones over an intercom. This paper grants insight to the designing and building of one such device.
In the first chapter I showcase the existing, currently operational, decades-old devices. I examine their principles of operation and the services they provide and point out how they fall short of actual modern user needs.
I created my own device with a Linux-based single-board computer. In the second chapter I present its auxiliary circuit that is based on an 8-bit microcontroller. I articulate upon how the firmware that runs on the microcontroller works, as well as how the different parts communicate with each other. Then I go on to describe higher-level implements. I give a detailed description of the timer and player program that I wrote in in C++ and of the structure and setup of it. Lastly, I talk about the browser-based user inferace and the backend working behind it.
Finally, I summarise my experiences of the project and ponder about a few future plans.