Car alarm Car alarm A car alarm is an electronic device installed in a vehicle in an attempt to discourage theft of the vehicle itself, its contents, or both. Car alarms work by emitting high-volume sound (often a vehicle-mounted siren, klaxon, pre-recorded verbal warning, the vehicle's own horn, or a combination of these) when the conditions necessary for triggering it are met. Such alarms may also cause the vehicle's headlights to flash, may notify the car's owner of the incident via a paging system, and may interrupt one or more electrical circuits necessary for the car to start. Although inexpensive to acquire
Train horn regular loud operation for general use. Train horn A train horn is a powerful air horn that serves as an audible warning device on electric and Diesel locomotives. The horn's primary purpose is to alert persons and animals to an oncoming train, especially when approaching a grade crossing. The horn is also used for acknowledging signals given by railroad employees, such as during switching operations. Trains move on fixed rails, making them uniquely susceptible to collision. This susceptibility is exacerbated by the enormous weight and inertia of a train, which make it difficult to quickly stop when encountering an obstacle.