Monthly Archives: December 2009

Mechanical School Bell

Mechanical School Bell

Someone made lights turn on and off with a mechanical timer, then someone else thought, I can make it operate the School Bells. This is how it started. There has been many variations of this timer since about the mid 50′s using a mechanical clock using cams to trigger a micro switch. I remember in college the deputy principle had the job of looking after the  school bells. It was a mechanical clock timer, I remember him altering it every tuesday for assembly day because it was different timetable to the other days. If each days timetable was different it would be a chore setting it for each day. He would have need to revert it back the next day.  He was the only one that knew how to adjust it. It had a set ring duration and had a setting for every 5 minutes. You needed good eyesight to see where to slide in the pin, because it was a 24 hour cycle on the dial.

Electric School Bells

Electric School Bells

What a great invention by Joseph Henry (the father of inductance), they are so good and simple plus use very little power. There was an electric bell at Oxford University that rang for over 150 years. This would suggest electric bells are very reliable. Electric Bells for schools come in various sizes and voltages AC and DC. If you are looking for an Electric Bell make sure you get a Bell rated for outdoors (i.e. being waterproof). When electric bells are used in schools it is very easy to press the button and all the bells ring at once. Then came the smart bell, i.e the no hands model.