Alarms, Buzzers, and Sirens are devices that produce an audible signal usually like a steady high-pitched hum that is encased within a molded housing. The characteristics are driver circuitry, input type, voltage rated, voltage range, frequency, technology, operating mode, current supply, and port location. The technology is electromechanical, magnetic, piezo, and piezo (with feedback) with a frequency from multiple, 200Hz to 8kHz.