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 most recent essay film, Visual Disturbances, premiered in the open access journal [in]Transition yesterday. This open access journal features peer reviewed academic video essays and showcases a wide variety of film and media analysis. Visual Disturbances uses some cutting-edge eye tracking visualizations to explore how film audiences both perceive and mis-perceive movies.
Electronic Grenade's "'Computer' Mouse" project fits a fully functional computer into a fully functional, 3D printed mouse; the computer is a Raspberry Pi Zero W, with a teeeny leeetle flip out keyboard and a tiny little itsy bitsy flip-out screen. (via Motherboard)
The European Parliament is meeting this week, and the committee that will decide the future of the controversial new Copyright Directive will meet next, and depending on what they do, it might be the end of the road for the internet as we know it.
Looking for a career in music behind the boards, either as a music producer or DJ? It’s a good bet that you’re going to be working with Ableton Live. Each new iteration of this powerful workstation gives the user more tools to create, and it’s just as well suited for the task of meticulous track […]
The graveyard of failed startups is littered with concepts that just got lost in translation. At its core, that’s what great front-end design is about: Making an app or website usable, translating its best ideas smoothly to the user. It’s a skill so broad there might be no one book or course that covers it […]
Robotics: It’s a field that used to exist only as science fiction. Now it’s science fact, and it’s not just a playground for MIT prodigies. Thanks to the ROS (Robot Operating System) framework, anyone willing to learn robotics can practice robotics. And the easiest way to learn ROS? The Complete Robotics eBook Bundle. Combined, the […]