Buzzers typically provide a user with an alert when a given condition within the circuit has occurred. Applications for using buzzers include home appliances (dryer or refrigerator) and automobiles (keys in the ignition). They are based on either piezoelectric, ceramic, or magnetic technology. Two key parameters used in buzzer specifications are the frequency of sound they produce and their sound pressure level (SPL). TDK’ s buzzers have SPL ratings measured by a microphone at a distance of 10cm.