If you ever connected to the Internet before the 2000s, you probably remember that it made a peculiar sound. But despite becoming so familiar, it remained a mystery for most of us. What do these sounds mean?
As many already know, what you’re hearing is often called a handshake, the start of a telephone conversation between two modems. The modems are trying to find a common language and determine the weaknesses of the telephone channel originally meant for human speech.
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The first thing we hear in this example is a dial tone, the same tone you would hear when picking up your landline phone. The modem now knows it’s connected to a phone line and can dial a number. The number is signaled to the network using Dual-Tone Multi-Frequency signaling, or DTMF, the same sounds a telephone makes when dialing a number.
The remote modem answers with a distinct tone that our calling modem can recognize. They then exchange short bursts of binary data to assess what kind of protocol is appropriate. This is called a V.8 bis transaction.
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Some awesome long-lost stuff there 🙂 I certainly remember modems, all the way back to 2400BPS (my first one) and using slower ones at 1200 and 300 as well. An amazingly long way we’ve come.
Some awesome long-lost stuff there 🙂 I certainly remember modems, all the way back to 2400BPS (my first one) and using slower ones at 1200 and 300 as well. An amazingly long way we’ve come.