Task: Question Answering
Input (English): As the Earth passes through the tail of a comet, previously inanimate objects (ranging from weapons to electric signs, electronics, vehicles, lawnmowers, an electric knife, etc...) suddenly spring to life and turn homicidal. In a pre-title scene, a man (King in a cameo) tries to withdraw money from an ATM, but it instead calls him an "asshole", and he whines to his wife (King's real life wife Tabitha). Chaos soon begins as machines of all kinds come to life and begin assaulting humans: a drawbridge inexplicably raises during heavy traffic, resulting in multiple accidents, most notably a black AC/DC van and a watermelon truck; while at a Little League game, a vending machine kills the coach by firing canned soda point-blank into his groin and then to his skull; a driverless steamroller flattens one of the fleeing children, but one named Deke Keller manages to escape on his bike.The carnage spreads as humans and even pets are brutally killed by lawnmowers, chainsaws, electric hair dryers, pocket radios, and RC cars. At a roadside truck stop just outside Wilmington, North Carolina, a waitress is injured by an electric knife and arcade machines in the back room electrocute another victim. Employee and ex-convict Bill Robinson begins to suspect something is wrong when suddenly marauding big rig trucks, led by a black semi-truck sporting a giant Green Goblin mask on its grille, run down two individuals (including Deke's father) and trap the rest of the civilians inside the truck stop's diner.Robinson rallies the survivors; they use a cache of firearms and M72 LAW rockets stored in a bunker hidden under the diner and destroy many of the trucks. The trucks fight back in the form of a M274 Mule firing its post-mounted M60 machine gun into the building, killing several including the waitress when she rants at them. The vehicles then demand, via sending morse code signals through their car horns, that the humans pump their diesel for them in exchange for keeping them safe; the survivors soon realize they have become enslaved by their own machines. Robinson suggests they escape to a local island just off the coast, on which no vehicles or machines are permitted.During a fueling operation, Robinson sneaks a grenade onto the Mule vehicle, destroying it, then leads the party out of the diner via a sewer hatch to the main road just as the trucks demolish the entire truck stop. The survivors are pursued to the docks by the Green Goblin truck, which manages to kill one more trucker after he steals a ring from a female corpse in a car before Robinson destroys the truck once and for all with a direct hit from an M72 LAW rocket shot. The survivors then sail off to safety; a title card epilogue explains that two days after the machines' rampage, a UFO was destroyed by a Soviet "weather satellite" conveniently equipped with class IV nuclear missiles and a laser cannon., Question: How do the vehicles send their demands ?
Output (English): Answer: The vehicles send their demands through morse codes using their car horns.