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
Jen "Klingon Pop Warrior" Usellis records covers of pop songs, translated into Klingon, the apex of which is surely her rendition of "Let it Go" ("yIbuSQo'") from Frozen. (via Borderlands)
The Lixada LED Handheld Flashlight is a $9 stocking-stuffer ($29 for 4): a six-LED/36 lumen flashlight that clips directly over the terminals of a 9V battery, forming an easy flashlight rated for up to 10,000 hours (battery life depends on whether you're switched to 6, 4 or 2 LEDs). One reviewer uses 9V batteries swapped […]
3D printing is a dumpster fire of stupid, obvious patents, but thankfully many of these are expiring; this year, the stupid patent on putting sides on a 3D printer (extrusion printers are very sensitive to errant breezes and just a puff of wind can ruin a print that took hours, just minutes before it completes).
So you missed Black Friday and Cyber Monday? Well, there’s one more holiday milestone coming up: Green Monday, on Dec. 16. It’s one of the busiest online shopping days for the simple reason that it will be 10 days before Christmas, which is when last-minute shoppers start to stress. Our advice? Don’t wait for that […]
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Walk through any office, and you will likely spot a few bobbleheads. These wobbly figurines are great fun to have around, although most celebrate people we will never meet. For something a little more personal, try Handmade Custom Bobbleheads. These mini caricatures are sculpted and painted by skilled artisans, based on any photo you provide. […]