Those old Whistle, the Chirps and the buzzes: The Dial – Up Modems

Dial – Up modems are noisy. But, why?

The 1990’s have heard loads of those screeching and whistling noise of their dial-up modems, when trying to connect to the amazing world of the internet. Those starting noisy sessions mainly marked the handshake of the basic dial – up modem. But what did that fight between the electronic disturbance mean?

Now, the percent of the market using the dial-p modems have reduced from 100% in the 1990’s to only about 10% or less in the present days. But yes, that sound really causes a feeling of nostalgia to all the coders and the computer addicts. Let us see, what that noisy really was.

The terrible, or must I say nostalgic, tone was heard only when we first connected to the internet. Once we were connected, there were no further such noises, even though we still have reserved the phone line for accessing the internet. So what is it with the initial noisy part, and then the silence?

The Mystery Unveiled

What were the modems actually designed for? The basic idea in the mind was to allow us o send data over the network, which was mainly designed to carry the voice. This is the main reason for the communication method between the two modems required it to be in the audible hearing range; else, it would have not been possible for them to be carried over the phone line. The current system uses the DSL lines, which can carry both the data and the voice.

The nostalgic sound has always been there, one just had to pick the receiver up to listen to them. While connecting to the internet, these noises were played on the loudspeaker, so that you may know if something went wrong with the connection, such as if you get a busy signal, and similar cases.

The sounds and the noises which we heard from the modem is the test of the telephone quality line. The modem has a set of precise and specific sounds which it sends, and is heard by the other end. This way, the modems could get an idea as to how clear is the line between the two modems. It also realizes the type of frequencies it may send over the communication line. The basic rule is, the more the frequencies which can be used in the communication process, and lower the noise over the communication line, faster is the speed at which the communication may happen.

If any connection failure has to occur, it occurs during this handshaking stage process. The reasons for failures may be busy line, or the unavailability of a modem on the other end.

Initially, modems were configured to play the handshaking sequence loudly. Such a configuration was done by sending a command during the setup, “AT M1” to the modem. In the alternate manner, the command “AT M2” leaves the speaker to be in the on state all the time. In turn, “AT M0”does not turn the speaker on at any time.

If you ever picked up the phone during some active session, then the transmission noise which you would actually hear would simply sound like static, instead of that loud noise during the handshaking process.

The “AT M0” command is like having the power of the invisibility cloak for stealth browsing in the night time.

High baud traffic creates sound of static. But the story of very low baud modems is different. At low bauds, you may even hear the incoming data. The reason for the static sound on hiher baud rates is that they use data-scrambler, which makes most of the patterns of the data to be indistinguishable audibly.

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