The modem is the device that connects your computer to the telephone line. It converts digital signals into analog ones so your computer can talk to the telephone company. The modem is usually located in your computer, but it can also be found in some routers and other networking devices. ..
Today’s Question & Answer session comes to us courtesy of SuperUser—a subdivision of Stack Exchange, a community-drive grouping of Q&A web sites.
While dial-up modem use might be down from the nearly 100% market saturation in the 1990s to only 10% of current US internet users, the sound of a dial-up modem connecting lives on in the memories of geeks everywhere. This week we’re taking a look at the technology behind the noisy process and what exactly was going on when you dialed in for your internet session.
The Question
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SuperUser reader Celeritas poses the question surely millions of people have asked themselves over the years:
Why indeed? What was going on during the noisy part and why the silence afterwards?
The Answers
Several SuperUser contributors fleshed out an answer for us. Scott Chamberlain writes:
Tylerl expands on that and explains how you could manipulate your modem to pipe down:
The sounds were there all the time, you just needed to pick up the phone to hear it. The reason they played it over a loudspeaker to start with is so you could hear if somthing went wrong with the connection (busy signal, wrong number, a person picked up instead of a modem on the other end, etc).
Oh the magic of AT M0; discovering that command was like being given an invisibility cloak-stealthy late night browsing for everyone. While Tylerl notes that high-baud traffic sound just like static, contributor Supercat notes that very low-baud modems were a different story:
If a connection ever failed due to connection quality, it would generally fail during this initial handshake process. And if you were listening, you could usually tell why (e.g. you got an answering machine on the other end instead of a modem).
As such, modems were usually configured to play this handshake sequence out loud. This was configured by sending AT M1 to the modem during setup. Alternately, AT M2 means to leave the speaker on all the time, while AT M0 means don’t turn the speaker on at all. See the AT command set for more information.
The actual transmission noise that you would hear if you picked up the phone during an active session (as opposed to during this handshake procedure) just sounds like static.
Have something to add to the explanation? Sound off in the the comments. Want to read more answers from other tech-savvy Stack Exchange users? Check out the full discussion thread here.
