Phreaking Phones with a Voice Recorder

Related link: http://www.uneasysilence.com/archive/2005/05/3065/

While assembling today’s news items for the O’Reilly Digital Audio site, I came across an interesting article about making free phone calls with an iPod. (Thanks to Hack a Day for the link.) Basically, you download some WAV files, make playlists in your ’pod, and then blare them into a defenseless payphone. (Some of the WAVs duplicate the confirmation tones the phone generates when a caller inserts a coin; others duplicate the sounds of the 0–9 buttons.)

The process, called phreaking, is illegal of course, but has been a classic hacker challenge for almost 50 years. In his salad days, Apple Computer co-founder Steve Wozniak reportedly tried to call the Pope in Rome for free with a homebrew gadget.

Legal issues aside, it’s so hard to find a payphone these days that you’d probably be better off using VoIP to make your free calls. But then my eyes lit on the Olympus DS-2, the high-quality digital voice recorder I’d recently reviewed, and I got an idea.

Downloading the WAVs from the Phreaks and Geeks site, I pasted the seven tones representing a friend’s cell phone number into a new document in my audio editor. I separated the tones with blank spaces (via the Insert Silence command) that were the same length as the individual tones. Then I held the telephone receiver up to the computer speaker and hit Play.

“We’re sorry! Your call could not go through as dialed.”

Remembering a line on the original site about putting five-second gaps in the playlist, I added more space between the tones (about a quarter of a second total). It worked!

Then I held the DS-2 voice recorder up to the speaker and recorded the sequence. Holding the DS-2’s speaker up to the phone, I was able to dial successfully again. Because the DS-2 lets you name your recordings, I titled the toneburst with my friend’s number.

I later remembered that Palm Desktop software can also generate touch-tones from entries in your address book. Recording that sequence off the computer speaker into the DS-2’s mic was a lot faster than assembling the tones in the audio editor, although the Palm sequence played back more slowly.

Of course, carrying touch-tones around in a voice recorder is kinda silly if you also have a cell phone, but I often forget my phone whereas I almost always carry my voice recorder. And it’ll surely make a good party trick. Now, where did I put the Pope’s number?

What’s on your phreakin’ iPod?