600m Range 30W Megaphone/Loud Hailer with Siren & Microphone - Speech/Voice Amp - Loops

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Twenty years earlier, Kircher described a device that could be used as both a megaphone and for "overhearing" people speaking outside a house. His coiled horn would be mounted into the side of a building, with a narrow end inside that could be either spoken into or listened to, and the wide mouth projecting through the outside wall. Prescott, George B. Bell's Electric Speaking Telephone: Its Invention, Construction, Application, Modification, and History. New York: D. Appleton &, 1884.

Montgomery, Henry C. (1959). "Amplification and High Fidelity in the Greek Theater". The Classical Journal. 54 (6): 242–245. JSTOR 3294133.A small compact megaphone that uses very high frequencies that penetrate and carry, while using little power, up to 700 metres. Very economical on batteries

FITTED WITH BLUETOOTH +RECHARGEABLE LITHIUM ION BATTERIES 8,800ma; OR USE WITH CAR CIGARETTE LIGHTER; CONNECT MULTIPLE SUPER PEARLS SIMULTANEOUSLY; 12 MONTH GUARANTEE; VOICE+SIREN R3900 Each intercom's channel can be renamed. This allows you to customize the channel's name so you know who your are talking to. A megaphone, speaking-trumpet, bullhorn, blowhorn, or loudhailer is usually a portable or hand-held, cone-shaped acoustic horn used to amplify a person's voice or other sounds and direct it in a given direction. The sound is introduced into the narrow end of the megaphone, by holding it up to the face and speaking into it, and the sound waves radiate out the wide end. A megaphone increases the volume of sound by increasing the acoustic impedance seen by the vocal cords, matching the impedance of the vocal cords to the air, so that more sound power is radiated. It also serves to direct the sound waves in the direction the horn is pointing. It somewhat distorts the sound of the voice because the frequency response of the megaphone is greater at higher sound frequencies. This week we are looking at two words which may be confused by learners of English: scarce and scarcely. Improve your English with Collins. The letter H can be useful to create some two-letter words but there are some longer, high scoring words too. Here are some examples.Four foghorn signals can be used depending on the conditions, or use the bells, whistles, horn or siren.