Patterns in the DTMF Number Pad

Data Representation, Metashapes

Today I am continuing on my interest in the tones used by wired telephony and the patterns made by same. I’ve managed to turn the tones used in the DTMF numberpad into visual representations and have started playing with the interactions between them.

Some background: when you hear a “TouchTone™” sound, you’re hearing two set frequencies played together that lets the switching equipment know what number you have selected. There is a 4×4 grid of these frequencies that creates a unique identifier for all the numbers on the telephone dialing buttons, as well as the star and pound keys. These frequencies were selected so that there are no easy multiples or common denominators between them, and so there is a definite gap between the highest of the low frequencies and the lowest of the high frequencies. Also, there are four extra “numbers” that are not used by consumers, which in some applications would allow the caller to select a call priority level (mostly used by the military) or activate special actions in the phone switch (used by telephone linemen). All of these numbers are arranged like this, with the lowest frequencies in the upper left and the highest frequencies in the lower right:

1 2 3 A
4 5 6 B
7 8 9 C
* 0 # D

(Of course, all this is quite wonky and is basically just part of my process for creating the following patterns. Please enjoy these as visual creations, and ignore the preceding telephonic geekery if you wish!)

First one is a simple interaction of grayscale lines with 50% transparency:

The second is the simple interaction between blue and yellow lines, also with 50% transparency:

More should be coming soon!

DTMF Made Visible

Data Representation, Metashapes

Another bit of noodling I did over the past few days, I’m playing with the frequency mapping of the DTMF (or TouchTone™) sounds used in telephony. These tones are becoming less and less prevalent as mobile phones replace land lines, so this is something of a latter-day portrait of a mature technology. The colors are okay, but I’ll probably play with them some more. Pictured here are the ringback tone, dial tone, and busy signal. I’ll do the numberpad presently.

Full Kendall-MIT MBTA Station Icosacomposite

Icosacomposite Video, Infrastructure

As luck would have it, I was able to get to Kendall-MIT yesterday morning and shoot a full 50 minutes of footage. Here’s the new composite:

Funny thing—when you layer time-based media, there’s always a small but non-zero chance that periodic events will synch up in the composition. This is the case here: in some of the layers, the automated station calls for the trains managed to line up pretty closely, resulting in passages that are much clearer than normal, but overlaid with flange and echo effects as the synchronization is not perfect.