communication a matter of seconds. The mobile phone was invented in 1973 by Dr. Martin Cooper, a Motorola employee. On April 3, 1973, the first cell phone call was made. The caller was naturally, Dr. Cooper himself. Prior to the development of mobile phones, people used two-way radios to communicate while they were mobile. The idea behind two-way radios gave rise to the invention of mobile phones. During the 1940s, Motorola came up with the Walkie-Talkie followed by handheld two-way radios that operated on battery power. In 1947, Douglas Ring and W. Rae Young at Bell Labs introduced the idea of hexagonal cells for mobile phones. Ericsson came up with an automatic mobile phone system, which was released in Sweden in 1956. The drawback of this system was that the phones weighed 40 kg´s. Till 1970, mobile phones had to remain within their cell area and there were no means to continue communication while switching between cell areas.
TUSCALOOSA, AL TORNADOES NASHVILLE, TN - FLOODING HISTORY Story begins in the early 1920s with an inventive scientist named Samuel Ruben and Philip Rogers Mallory During World War II, for instance, Ruben devised the mercury cell, which packed more capacity in less space and was durable enough for the harsh climates of wartime theaters like North Africa and the South Pacific--places where ordinary zinc carbon batteries used in flashlights, mine detectors, and walkie-talkies couldn't hold up. P.R. Mallory manufactured millions of mercury cells for the war effort. The Mallory Battery Company was formed shortly thereafter. And in 1950s they improved that battery, making it more compact, durable, and longer lasting. And now they are the world's leading producer of high-performance alkaline batteries. RESOURCES http://www.duracell.com/en-US/company/index.jspx https://www.google.ee/search? q=duracell&rlz=1C1AFAB_enEE445EE445&aq=f&um=1&ie=UTF-
letters or memos predates the creation of the Internet. Pictures, documents and other files are sent as email attachments. Emails can be cc-ed to multiple email addresses. Internet telephony is another common communications service made possible by the creation of the Internet. VoIP stands for Voice- over-Internet Protocol, referring to the protocol that underlies all Internet communication. The idea began in the early 1990s with walkie-talkie- like voice applications for personal computers. In recent years many VoIP systems have become as easy to use and as convenient as a normal telephone. Data transfer File sharing is an example of transferring large amounts of data across the Internet. A computer file can be emailed to customers, colleagues and friends as an attachment. It can be uploaded to a website or FTP server for easy download by others
7. Because of the alarm failed to work during a drill, our security system is under the microscope. 8. He knew how to push the right buttons, exploiting her sense of guilt to get his own way. LANGUAGE FOCUS V 1. Inside a computer you will find several circuit boards. 2. When you save your work on a computer, it is stored on one of its storage devices the hard disk, the floppy drive or the CD-ROM. 3. It's a mobile phone, but it can be used as a walkie-talkie, too. It's quite an interesting little gadget. 4. A laptop is easy to carry with you, but it's not as powerful as a proper desktop computer. 5. A word processor is a software application which helps you type, format and edit texts. 6. Before attempting any repairs, make sure you have cut off the power source. 7. Text messaging has gained popularity over the last few years, becoming one of the most common forms of communication. 8
Ümber juhtme tekivad magnetväljad, mis on vastassuunaline. Magnetväli on ainult juhtmete vahel, eemal on tasakaalus, mistõttu ei tekita väljas häireid (magnetväljade jõujooned on vastassuunalised). Võrgukaablis on 4 keerdpaari, tavaliselt kasutatakse aga ainult ühte. o Simpleks – ühesuunaline side. Saadetakse signaal teele, vastu ei tule midagi. o Dupleks – kahesuunaline side. Pooldupleks – walkie-talkie. Samal ajal ei saa edastada, aga kordamööda – vastassuunaline side on võimalik (piisab 1st kaablist) Täisdupleks – telefon – saab samal ajal rääkida – andmed jooksevad samal ajal erinevates suundades. UTP – unshielded twisted pair STP – shielded twisted pair CAT – kategooria näitab kvaliteeti. Mida suurem on number, seda parem on
1. Üldine kommunikatsiooni mudel Rr Kommunikatsioonisüsteem ei tee vahet sellel mida me täpselt edastame (video, heli, pilt jne kõik tõlgitakse ikkagi 1 ja 0 jadaks) Simplex - ühesuunaline Pool-Duplex - mõlemat pidi, aga korda mööda, walkie-talkied, ainult üks saab korraga andmeid edastada Täis-Duplex - mõlemat pidi ja samal ajal, telefonid Süsteemi rrRrrrrr on infovahetus, seega meil on: Allikas - Saatja - Edastaja - Vastuvõtja - Sihtpunkt Allikas - genereerib edastamiseks vajaliku infoex Saatja - kodeerib allika poolt genereeritud info signaaliks (ADC nt kui edastame heli) Edastaja - vastutab signaali transportimise eest punktist A punkti B Vastuvõtja - dekodeerib saadud signaali sihtpunkti jaoks arusaadavasse vormi
cryptographic applications. Using such esoteric tools as Galois field theory, stochastic processes, and group, matrix, and number theory, ________*w».»ui,ai iiiuuci 01 a proposed cipher machine and will simulate its operation on a computer, thus producing the cipher without having to build the hardware. Rotor principles have often been tested for cryptographic strength in this way. It devises audio scramblers, from the ultra-secure types for high officials to the walkie-talkies of platoon commanders, as well as video scramblers for reconnaissance television and for facsimile. Their development involves sciences from metallurgy to optics, as well as techniques— important in miniaturization—from printed circuits to ferro-resonance. R/D's third section, RADE (for "Research And DEvelop-ment"), conducts basic transmission research, going deeply into such matters as the interaction of electromagnetic radiation and matter. It aims both at
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