Martinshorn, signal horn on an emergency vehicle, compressed air

Sign, 14x10, Air Horn, 3 Blast First Aid, 1 Long for Fire

Emergency vehicle hi-res stock photography and images - Alamy

Yosoo Electronic Martin Horn for Car Music Trumpet Chrome Plated Double Trumpet with Air Compressor for Car Steamship 12V Horn Car Horn Universal : : Automotive

Horn signal hi-res stock photography and images - Alamy

MARTIN HORN 2298 GM-Max B Martin(Made in Germany)

SAFETY-SPORT Personal 911 AIR Horn : : Sports & Outdoors

Large Air Horn

Safety Sport Admiral Air Horn 8oz

Loud air horn hi-res stock photography and images - Alamy

Ambulance siren hi-res stock photography and images - Alamy

Martinshorn, signal horn on an emergency vehicle, compressed air fanfare, ambulance, signal horn, siren Stock Photo - Alamy

What is the sound/device/mech. that emergency vehicles use to produce the electronic 'horn' sound? I don't mean one of the siren types- hi/lo, whelp, etc. I am talking about the short and