A buzzer is an electronic device that produces a buzzing or beeping sound. It is commonly used in various applications such as alarms, timers, and notification systems. Buzzers can be of different types, including piezoelectric, electromagnetic, and mechanical. They are simple yet effective in providing audible signals.

A reversing alarm is a security device installed on automobiles to warn pedestrians and other road users while reversing. These alarms produce a loud and distinct sound, alerting those in the vehicle's blind spots. They help to prevent accidents and enhance safety.

car horn is a sound signalling device used most commonly on motor vehicles. The horn alerts other road users to the vehicle's presence and can indicate a driver's intentions. Different types of horns are available, including electric, pneumatic, and mechanical. The use of the horn is subject to local traffic regulations.