Oona Räisänen has written a thorough and engrossing article about the noises emitted by dial-up modems while they connect and handshake, and the accompanying graphic (ZOMG HUGE) is nothing short of spectacular. It would make a great full-size poster -- maybe a framed art-print.
Now the modems must address the problem of echo suppression. When humans talk, only one of them is usually talking while the other one listens. The telephone network exploits this fact and temporarily silences the return channel to suppress any confusing echoes of the talker's own voice.
Modems don't like this at all, as they can very well talk at the same time (it's called full-duplex). The answering modem now puts on a special answer tone that will disable any echo suppression circuits on the line. The tone also has periodic "snaps" (180° phase transitions) that aim to disable yet another type of circuit called echo canceller.
Now the modems will list their supported modulation modes and try to find one that both know. They also probe the line with test tones to see how it responds to tones of different frequencies, and how much it attenuates the signal. They exchange their test results and decide a speed that is suitable for the line.
After this, the modems will go to scrambled data. They put their data through a special scrambling formula before transmission to make its power distribution more even and to make sure there are no patterns that are suboptimal for transfer. They listen to each other sending a series of binary 1's and adjust their equalizers to optimally shape the incoming signal.
The sound of the dialup, pictured
My UK publisher, Head of Zeus, has published the official tour schedule for the British tour for Walkaway, with stops in Oxford (with Tim Harford), London (with Laurie Penny), Liverpool (with Chris Pak), Birmingham, and the Hay Literary Festival (with Dr Adam Rutherford). Hope to see you there!
My publicist just found an extra box of the cool promotional Walkaway multitools, and she’s generously offered to give them to the next 100 people to reserve tickets to the May 7th Walkaway event at Chicago’s Royal George Theater, where I’m presenting with CARDS AGAINST HUMANITY creator Max Temkin (current ticket-holders, don’t worry, you get […]
Carol from Cheapass Games writes, “In our continuing quest to bring back the very best classic Cheapass Games, we’re creating a new boxed set of Button Men, our strategy dice combat game. This time around, the characters will appear on cards, rather than pin-back buttons, but since they’re all 1950s era gangsters, the ‘button men’ […]
All moms are different. But all moms like getting flowers on Mother’s Day, and that’s a fact (not, however a fact we can document in any fashion.) Instead of getting chewed out for forgetting to call her on the second Sunday of May, you can take care of it ahead of time with Teleflora’s flower […]
Yeah, Bluetooth audio is pretty common these days, so why should you care about these earbuds? Look how happy that woman up above looks. She’s got FRESHeBUDS in. Boom. There’s your reason. She’s also at the beach and it appears to be a very nice day.But for the sake of promotion, wireless earbuds are fast becoming the […]
“Gets stuff done,” is a good way to be described by anybody. Especially by coworkers or bosses. Because whether you’re in finance or a children’s librarian, stuff needs to get done. But how do you make sure stuff gets done? You definitely can’t do all the stuff yourself, unless your company/organization/government office consists entirely of you. And […]