SMC291 Abramson Reading

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St. Michael's College Courses
Jennifer Harris

Invention of TV 2122012 123200 AM y TV electric transmission and reception of transient visual images prob first invention by a committee in sense of resulting from efforts of hundreds of individuals widely separated in time and space all prompted by urge to produce system of seeing over horizon y First practical solution to instant communication telegraph machine with Morse code transmitted over wires at almost speed of light y Transmission of symbols Frederick C Bakewell 1847 transmitting handwriting metal foil with ink around cylindery Caselli 1855 using actions of pendulums stylus tracing object and electrically turned on or off as scan message y Scanning of simple figures important involve two foundations of later system of instant visual transmission y Sequential scanning dissecting picture y Means to synchronize transmitter with receiver y Primitive machines do work limited value at time lead to more important in future y Copytelegraphs today as phototelegraphy or facsimile fax y Next step transmission of audio over same wires y Alexander Graham Bell 1876 transmit sound of voice three means of instant communications telegraph copytelegraph and telephone time ripe for intro of visual comm y 1873 Smith and May selenium rods charge resistance conductivity when exposed to varying light certain metals reacting to changes of light intensity y 1878 combination of telephone and Edisons phonograph 1877 combined with progress in photographymagazine cartoon of new Edison inventiontelephonoscope twoway visual system on wide screen depicting parents speaking with daughter via electric camera obscura and telephone depicted before he invented motion picture cameray LeBlanc ingenious method of transmitting moving images over electrical wire 1880 scanning device consisting of vibrating mirrors at different speed light from image sent to transducer converted into electricity receiver with two mica as shutter moved according to signal to control light suggest because of persistence of vision possible to build of likeness of transmitted imagepaper contain all emlements for practical visual transmission system y 1884 Nipkow patent for German electric telescope revolving aperture disc Nipkow disk synchronization presumed by constant rotating speed all elements for successful visual transmission and soon followed by other ideas based on rotating disk y equipment with electrical discharges inside evacuated glass tubes Plucker sealed glass tube filled with gas ionized with certain voltage flow current glow colours Geissler tube yy Cathode Ray Tube y 1900 paper Television describe apparatus based on magnetic properties of selenium new term slowly supplant older names of telectroscope and telephot to describe newly born art and science of seeing at a distance y theories create much controversy in scientific community improbable vs possible y Swinton distant electric vision possible with cathode ray tubes synchronized and with means for converting lighteleclight first suggestion of use as image transmittery 1909 3 TV systems acutally built and operated sty 1 not rweally television because transmitter form of telegraph sender not transducer of light to elecDieckmann y second Ruhmer mosaic of cells in rows alternating current simple geometric figures shown multiwire simultaneous so not true TV y third demonstrated by Fournier and Rignoux selenium cells separate relays connected with rotating commutator modulated light sent through rotating mirror where image reconstituted on screen real TV system first on recordyy Rozing Zworykin Swinton y Rozing on Cathode Ray ststem Russian patent proposing TV using cathode ray tube as receiver two mirror drums for scanning and dissecting img receiver to cold cathode ray Braun tube at time no known way for modulating electron beam so ingenious modulated brightness by moving metal plates in accordance with incoming signal
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