Most common Warning Devices emit light or sound. They may be used ground, marine and air transportation.
The latest technology in warning lights is LED; it is the most reliable and uses less power. The most common lights are Beacons and Directional, which may be Rotating or Strobe and with the shape of a cylinder, minibar or full bar. There are also some to be hidden. They are available in several colors, the most used: White, Amber, Red and Blue.
In the field of sound devices, the electronic sirens together with a control box and a microphone, may also work as horns and speakers. They are also used to warn when vehicles are moving backward.
Lastly, video screens combined with cameras and proximity sensors & beepers, provide drivers of added safety when approaching tight spaces or for attaching a trailer to a Gooseneck or Rear Bumper Hitch.