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Walkie-Talkie (English)

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A walkie-talkie, or handie talkie, (more formally known as a handheld transceiver) is a hand-held, portable, two-way radio transceiver. Its development during the Second World War has been variously credited to Donald L. Hings, radio engineer Alfred J. Gross, and engineering teams at Motorola. Similar designs were created for other armed forces, and after the war, walkie-talkies spread to public safety and eventually commercial and jobsite work. Major characteristics include a half-duplex channel (only one radio transmits at a time, though any number can listen) and a "push-to-talk" (P.T.T) switch that starts transmission. Typical walkie-talkies resemble a telephone handset, possibly slightly larger but still a single unit, with an antenna sticking out of the top. Where a phone's earpiece is only loud enough to be heard by the user, a walkie-talkie's built-in speaker can be heard by the user and those in the user's immediate vicinity. Hand-held transceivers may be used to communicate between each other, or to vehicle-mounted or base stations.
The first radio receiver/transmitter to be widely nick-named "Walkie-Talkie" was the backpacked Motorola SCR-300, created by an engineering team in 1940 at the Galvin Manufacturing Company (fore-runner of Motorola). The team consisted of Dan Noble, who conceived of the design using frequency modulation, Raymond Yoder, Henryk Magnuski who was the principal RF engineer, Marion Bond, Lloyd Morris, and Bill Vogel.

SCR-536 "handie talkie"
Motorola also produced the hand-held AM SCR-536 radio during World War II, and it was called the "Handie-Talkie" (HT). The terms are often confused today, but the original walkie talkie referred to the back mounted model, while the handie talkie was the device which could be held entirely in the hand (but had vastly reduced performance). Both devices ran on vacuum tubes and used high voltage dry cell batteries. (Handie-Talkie became a trademark of Motorola, Inc. on May 22, 1951. The application was filed with the U.S. Patent and Trademark Office, and the trademark registration number is 71560123. )
Radio engineer Alfred J. Gross also worked on the early technology behind the walkie-talkie between 1934 and 1941, and is sometimes credited with inventing it. Gross had developed and tested a small portable high-frequency radio with two-way communications features which he dubbed a "walkie-talkie". The device caught the attention of the U.S. Office of Strategic Services (now the Central Intelligence Agency), which recruited him to develop the Joan-Eleanor system, a two-way, air-to-ground radio system for covert use by troops behind enemy lines during World War II. [1]


Also credited with the invention of the walkie talkie is Canadian inventor Donald Hings who created a portable radio signaling system for his employer CM&S in 1937 which he called a "packset", but which later became known as the "walkie talkie". Hings was formally decorated for its significance to the war effort.[2][3] Hing's model C-58 "Handy-Talkie" was in military service by 1942, the result of a secret R&D effort that began in 1940.
Following World War II, Raytheon developed the SCR-536's military replacement, the AN/PRC-6. The AN/PRC-6 circuit uses 13 tubes (receiver and transmitter); a second set of 13 tubes is supplied with the unit as running spares. The unit is factory set with one crystal and may be changed to a different frequency in the field by replacing the crystal and re-tuning the unit. It uses a 24 inch whip antenna. There is an optional handset H-33C/PT that can be connected to the AN/PRC-6 by a 5 foot cable. A web sling is provided.
In the mid-1970s the Marine Corps initiated an effort to develop a squad radio to replace the unsatisfactory helmet-mounted AN/PRR-9 receiver and receiver/transmitter hand-held AN/PRT-4 (both developed by the Army). The AN/PRC-68 was first produced in 1976 by Magnavox, was issued to the Marines in the 1980s, and was adopted by the US Army as well.
The abbreviation HT, derived from Motorola's "Handie Talkie" trademark, is commonly used to refer to portable handheld ham radios, with "walkie-talkie" often used as a layman's term or specifically to refer to a toy. Public safety or commercial users generally refer to their handhelds simply as "radios". Surplus Motorola Handie Talkies found their way into the hands of ham radio operators immediately following World War II. Motorola's public safety radios of the 1950s and 1960s, were loaned or donated to ham groups as part of the Civil Defense program. To avoid trademark infringement, other manufacturers use designations such as "Handheld Transceiver" or "Handie Transceiver" for their products.
http://en.wikipedia.org/wiki/Walkie-talkie

Walkie-Talkie (Italiano)

Da Wikipedia, l'enciclopedia libera.

Storia

Il primo walkie talkie venne originariamente sviluppato dal governo canadese durante la seconda guerra mondiale, dal canadese Donald L. Hings. Progetti simili vennero creati in altre forze armate. Finita la guerra i walkie-talkies si espansero nell'uso per la sicurezza pubblica e quindi in settori commerciali e di lavoro.

Il primo ricetrasmettitore soprannominato "Walkie-Talkie" fu lo spalleggiabile Motorola SCR-300. Motorola produsse anche la radio portatile AM SCR-536 durante la seconda guerra mondiale, che venne soprannominata "Handie-Talkie" (HT). (Handie-Talkie divenne un marchio registrato di Motorola negli Stati Uniti il 22 maggio 1951 con il numero di registrazione 71560123)

 


Descrizione

Le caratteristiche tipiche consistono nell'avere un canale di comunicazione half duplex e punto-multipunto: una sola radio può trasmettere in un dato momento, ma più radio possono sentire il messaggio. La trasmissione inizia premendo il pulsante push-to-talk, spesso abbreviato PTT.

Un walkie talkie assomiglia vagamente ad un telefono, di solito è più grande di un telefono cellulare, con un'antenna che spunta dall'alto. Mentre un telefono ha un altoparlante che può essere sentito solo da una persona, l'altoparlante di un walkie-talkie ha un volume più alto e può essere sentito da più persone nelle vicinanze.

I palmari possono essere utilizzati per comunicare fra di loro, con stazioni fisse o montate su mezzi di trasporto.

Fonte: http://it.wikipedia.org/wiki/Walkie-talkie