‘This is What a Dial Up Modem Connection Looks Like on the Spectrogram (DTMF Handshake and Call)

On April 21 2022, an Imgur account shared video of what was apparently a visual representation of “what a dial up modem connection looks like on the spectrogram,” a post that evoked nostalgia for those who populated the early internet:

One day prior, the same video was popular on Reddit’s r/interestingasfuck (with an identical title). It was also cross-posted to r/nostalgia:

Fact Check

Claim: "This is what a dial up modem connection looks like on the spectrogram (DTMF handshake and call.)"

Description: A post on Imgur and Reddit claimed to visually represent what a dial up modem connection looks like on the spectrogram, which includes DTMF handshake and call.

Rating: True

Rating Explanation: After thorough analysis and comparison with the content in an earlier video from 2013 and explanations from technical resources, the claim seems to accurately represent a dial up modem connection on a spectrogram.

Comments on both threads were similar to this one from Reddit:

Back in HS I used to download music on Napster over my 56k modem and then make mix tapes for my shitbox car using Winamp and my mom’s dual tape deck. I had to make sure nothing else was running on the PC to keep it from skipping while I was recording to the tape.

Now I have the internet in the palm of my hand with every song ever basically and it plugs into my truck… fuckin’ nuts.

Fuck… it just occurred to me I probably have files on my computer older than some of the kids on Reddit…

Although the clip’s sound and description were enough to generate significant engagement, neither really explained the origin or content of the video. Additionally, the clip was not new as of 2022 — a version of it was published to YouTube in 2013.

What is a Dial Up Modem Connection?

In the 1990s, internet users commonly accessed the web through a dial-up connection. Lifewire.com’s June 2021 “Is Dial-Up Networking Still a Thing?” explained:

Dial-up networking technology allows PCs and other network devices to connect to remote networks over standard telephone lines, and it is still available in some markets. When the World Wide Web exploded in popularity during the 1990s, dial-up was the most common type of internet service available, but much faster broadband internet services soon replaced it.

DTMF, Handshake, and Call

Both titles referenced a “DTMF handshake and call,” described on a tech site as the sounds a telephone makes when the numbers are pressed:

These tones are transmitted with the voice channel.

DTMF is used to control automated equipment and signal user intent, such as the number they wish to dial. Each key has two tones at specific frequencies … DTMF technology works by having the handset generate tones at specific frequencies and playing them over the phone line when a button is pressed on the keypad. Equipment at the other end of the phone line listens to the specific sounds and decodes them into commands.

In the above-linked Lifewire.com entry, a “handshake” was described in the context of dial-up connectivity:

Getting online via dial-up works the same today as it did during those early days of the web. A household subscribes to a service plan with a dial-up internet provider, connects a dial-up modem to their home telephone line, and calls a public access number to make an online connection.

The home modem calls another modem belonging to the provider (making a distinctive range of sounds in the process). After the two modems have negotiated mutually compatible settings, the connection is made, and the two modems continue exchanging network traffic until one or the other disconnects.

In 2013, a post to Reddit’s r/programming linked to a blog post explaining the “dialup handshake”:

What’s a Spectrogram?

The Pacific Northwest Seismic Network (PNSN) explained the function of spectrograms in the context of seismic activity:

A spectrogram is a visual way of representing the signal strength, or “loudness”, of a signal over time at various frequencies present in a particular waveform. Not only can one see whether there is more or less energy at, for example, 2 Hz vs 10 Hz, but one can also see how energy levels vary over time. In other sciences spectrograms are commonly used to display frequencies of sound waves produced by humans, machinery, animals, whales, jets, etc., as recorded by microphones. In the seismic world, spectrograms are increasingly being used to look at frequency content of continuous signals recorded by individual or groups of seismometers to help distinguish and characterize different types of earthquakes or other vibrations in the earth.

The Video

The r/programming post from 2013 linked (in comments) to a November 2012 blog post explaining each element of a similar visualization of dial up modem sounds:

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.

Hello, is this a modem?

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.


In short, a long-circulating video used a spectrogram (a visual way of depicting sound) to interpret audio of a dial up modem connecting to the internet. The sound itself was a “DTMF handshake and call,” frequencies signaling compatibility and subsequent connection. A 2012 blog post shared to r/programming explained a visualized audio of a dial up connection. April 2022 posts to Reddit and Imgur featured a video from 2013 or earlier, combining the instantly recognizable sound of a dial up modem connecting to the internet (typically followed by “you’ve got mail!”) Although broadband has long since become the most common way to connect to the internet, few early users forgot the distinctive sound of their computer connecting via dial-up.