Editing Buzzer (section)

===Electromechanical===
Early devices were based on an electromechanical system identical to an [[electric bell]] without the metal gong. Similarly, a [[relay]] may be connected to interrupt its own actuating [[Electric current|current]], causing the [[Switch|contact]]s to buzz (the contacts buzz at [[Utility frequency|line frequency]] if powered by [[alternating current]]) Often these units were anchored to a wall or ceiling to use it as a sounding board. The word "buzzer" comes from the rasping noise that electromechanical buzzers made.