{"id":30674,"date":"2019-10-31T21:36:50","date_gmt":"2019-10-31T18:36:50","guid":{"rendered":"https:\/\/prohoster.info\/blog\/50-letnij-modem-vzglyad-iznutri\/"},"modified":"2019-10-31T21:36:50","modified_gmt":"2019-10-31T18:36:50","slug":"50-letnij-modem-vzglyad-iznutri","status":"publish","type":"post","link":"https:\/\/prohoster.info\/da\/blog\/administrirovanie\/50-letnij-modem-vzglyad-iznutri","title":{"rendered":"50-\u00e5rigt modem: et indblik fra indersiden","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

\"50-\u00e5rigt
\n
\nFor several years, the author visited a flea market organized by W6TRW at the parking lot of Northrop Grumman in Redondo Beach, California. Among TVs resembling polar bears and numerous phone chargers and power supplies, a wooden box with a lock, a wooden handle, and a DB-25 connector on the side was visible. Next to the connector was a switch: half-duplex - full duplex. The author understood what it was. A modem. A wooden modem. Specifically - an acoustic coupler modem produced by Livermore Data Systems around 1965.<\/a><\/noindex><\/p>\n

\"50-\u00e5rigt
\n
\nThe modem was still at the flea market. Immediately after taking a photo, the author bought it for $20.<\/i><\/p>\n

Since not everyone knows what an acoustic coupler modem is, here's a brief history. The problem was that once upon a time, not only the lines belonged to the telephone companies. They also rented out the telephone devices. Readers who remember dial-up connected modems directly to phone lines. However, when this modem was made, that was prohibited. According to the American law of 1934, it was absolutely forbidden to connect anything to a home phone in any way. In 1956, following the case of Hush-A-Phone Corp v. United States, the rule was relaxed: mechanically<\/i> it became permissible to connect. Hush-A-Phone is her er hvad<\/a><\/noindex>.<\/p>\n

Formally, connecting various devices to the telephone line electrically was permitted in the U.S. in 1968 (the Carterphone decision<\/a><\/noindex>). However, until 1978, this opportunity could not be utilized since tariffs, specifications, and certification methods had not been developed. Therefore, from 1956 to 1978, it made sense to use acoustic coupler modems and answering machines. In practice, they were produced for a longer time \u2014 out of inertia.<\/p>\n

Denne modem, der nu st\u00e5r p\u00e5 forfatterens bord, er en uadskillelig, men us\u00e6dvanlig del af historien. Den blev fremstillet f\u00f8r Carterphone-udvalget, og derfor kan den ikke tilsluttes direkte til telefonnettet. Den er designet f\u00f8r mange af de chips, der i dag betragtes som klassiske. Den f\u00f8rste version af denne modem blev udgivet blot et \u00e5r efter Bell 103, den f\u00f8rste kommercielt succesfulde modem. Foran dig er et fremragende eksempel p\u00e5, hvor mange muligheder man kan 'udtr\u00e6kke' med blot tretten transistorer. Senere blev denne modem glemt i lang tid, indtil der blev lavet to videoer om den, en i 2009 og den anden i 2011:<\/p>\n

\r\n \"Afspil\r\n
<\/div>\r\n <\/div><\/center><\/p>\n

\r\n \"Afspil\r\n
<\/div>\r\n <\/div><\/center><\/p>\n

YouTuber phreakmonkey fik fat i et tidligt eksemplar af modemmet med et serienummer der er lidt over 200. Disse modemmer er kendetegnet ved kabinetter i valn\u00f8ddetr\u00e6, hvis dele er forbundet med 'swallowtails'. If\u00f8lge phreakmonkey kan man ud fra dette kendetegn vurdere, hvor gammel modemmet er, da 'swallowtails' kr\u00e6ver meget arbejde. Fra serienummer 850 begyndte modemmerne at blive placeret i teaktr\u00e6skabinetter med kasseforbindelser. Derefter begyndte kabinetdele at blive forbundet med notcher. Livermore Data Systems havde brug for at fremstille modemmer hurtigere og hurtigere.<\/p>\n

I 2007 kiggede bloggeren Brent Hilpert ind i en s\u00e5dan modem og beskrev dens opbygning<\/a><\/noindex>. Is\u00e6r dens kredsl\u00f8b er interessant. Alle tretten transistorer i modemmet er standard og var p\u00e5 det tidspunkt meget udbredte. En germanium PNP-transistor blev der brugt af grunde, som forfatteren ikke forst\u00e5r. Transistorer af alle disse typer er stadig let at finde i gamle lagre. For blot omkring tyve dollars kan man f\u00e5 et komplet s\u00e6t transistorer til at gentage en pr\u00e6cis kopi af modemmet. Desuden kr\u00e6ves der ogs\u00e5 andre komponenter, herunder miniaturetransformatorer.<\/p>\n

\"50-\u00e5rigt
\n
\nSelve akustiske koblingsenheden fra modemmet er blevet fjernet af nogen, resten svarer fuldt ud til dokumentationen. P\u00e5 krydspladen er der tre kredse. P\u00e5 den f\u00f8rste er alle dele af str\u00f8mforsyningen, undtagen transformatoren, p\u00e5 den anden modulatoren, p\u00e5 den tredje demodulatoren. P\u00e5 transistorerne 2N5138 er der en dato: uge 37 i 1969. Det har ikke v\u00e6ret muligt at fastsl\u00e5 den n\u00f8jagtige dato for modemmet, men det er sandsynligt, at det blev fremstillet og afsendt f\u00f8r 1970.<\/p>\n

\"50-\u00e5rigt
\n
\n\"50-\u00e5rigt
\n
\nNotch-forbindelsen betyder, at modemmet er af nyere dato<\/i><\/p>\n

\"50-\u00e5rigt
\n
\n\"50-\u00e5rigt
\n
\n\"50-\u00e5rigt
\n
\n\"50-\u00e5rigt
\n
\n\"50-\u00e5rigt
\n
\nForfatteren k\u00f8bte denne modem blot for at have den. Det er en tr\u00e6modem, men n\u00e6ppe nogen af forfatterens bekendte kan forestille sig, hvor cool den egentlig er. Det er et kunstobjekt med s\u00e5 meget us\u00e6dvanligt. Forfatteren ville reparere den, men inds\u00e5, at det var upraktisk.<\/p>\n

For det f\u00f8rste skal man finde den originale akustiske tilslutningsenhed. P\u00e5 grund af dens frav\u00e6r havde loppemarkedets bes\u00f8gende sv\u00e6rt ved at forst\u00e5, hvad de havde foran sig. Livermore Data Systems' logo og serienummeret var oprindeligt placeret p\u00e5 denne enhed, men nu gjorde deres frav\u00e6r det kun sv\u00e6rere for andre bes\u00f8gende at identificere varen som en modem, da de ikke er ansatte i computerhistoriske museer. Det kunne selvf\u00f8lgelig v\u00e6re fristende at printe delene til den akustiske tilslutningsenhed, men vil det overhovedet blive gjort?<\/p>\n

For det andet har mange af kondensatorernes parametre helt sikkert \"sluppet v\u00e6k\". Det ville v\u00e6re interessant at tage alle kredsl\u00f8bskortene fra hinanden, men hvis forfatteren \u00f8nsker at f\u00e5 en fungerende modem med akustisk tilslutning, er der en bedre mulighed.<\/p>\n

Det handler om en genial konstruktion kaldet «data toilet<\/a><\/noindex>«, udviklet af Chaos Computer Club i 1985 som svar p\u00e5 et lignende forbud, der dengang stadig var g\u00e6ldende i Tyskland. En s\u00e5dan modem er enklere i opbygning, men har flere muligheder. Den er bygget p\u00e5 en AM7910-chip, som stadig nogle gange kan findes til salg, og den arbejder med hastigheder op til 1200 Baud. Det er hurtigere at bygge et modem fra bunden p\u00e5 den end med diskrete transistorer.<\/p>\n

Generelt giver det ikke mening at genetablere denne tr\u00e6modem, men det var virkelig interessant at skille den ad, tage billeder af den og samle det hele, som det var. S\u00e5dan s\u00e5 n\u00e6sten al elektronikken indeni ud, f\u00f8r der blev indsat chips. Men hvis forfatteren pludselig skulle finde en passende akustisk tilslutningsenhed til denne modem, ville han selvf\u00f8lgelig overveje det igen: M\u00e5ske er det v\u00e6rd at tage fat p\u00e5 reparationen?
\n
Kilde: habr.com<\/a><\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"

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