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In Norse mythology, Gjallarhorn (Old Norse: [ˈɡjɑlːɑrˌhorn]; "hollering horn" [1] or "the loud sounding horn" [2]) is a horn associated with the god Heimdallr and the wise being Mímir. The sound of Heimdallr 's horn will herald the beginning of Ragnarök , the sound of which will be heard in all corners of the world.
Sirens often use horns to aim the pressure waves. This uses the siren's energy more efficiently by aiming it. Exponential horns achieve similar efficiencies with less material. The frequency, i.e. the cycles per second of the sound of a mechanical siren is controlled by the speed of its rotor, and the number of openings.
Train horns are sounded where a whistle post (marked with the letter "S" for siffler – "to whistle") is present. If the whistle post is labelled "J" (meaning jour – "day"), the horn is only to be sounded between 07:00 and 20:00. Horns must also be sounded when passing an oncoming train, and shortly before reaching the last car of the train.
Air-Raid alert signal on the civil defense alarm system: a siren sound of alternating pitch (between 280 Hz and 400 Hz) repeated three times in a row, lasting 30 seconds, with 30 second pauses between signals Emergency alarm signal: continuous siren sound with alternating pitch (between 133 Hz and 400 Hz) for 120 seconds
A fire alarm notification appliance is an active fire protection component of a fire alarm system. A notification appliance may use audible, visible, or other stimuli to alert the occupants of a fire or other emergency condition requiring action. Audible appliances have been in use longer than any other method of notification.
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The minimum amount of cardio exercise you can get away with each week depends on your resting heart rate and your specific fitness goals, according to trainers.
Hoard of the Dragon Queen and a second adventure, The Rise of Tiamat, pits the player characters against Tiamat. [2] [1]In an audacious bid for power the Cult of the Dragon, along with its dragon allies and the Red Wizards of Thay, seek to bring Tiamat from her prison in the Nine Hells to Faerun.