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Rob O’Hara on phreaking, Tesla coils and modems

Rob O’Hara posted a podcast about phreaking today. He explains in layperson’s terms how the phone system was controlled by tones, cites it as an example of security through obscurity, and he talks about his own first-person experience subverting the phone system. He was far from the only one who did that.

Rob made a side comment about people connecting generators to phone lines and wondering aloud why someone would do such a thing. The version of that story I always heard involved Tesla coils. The theory was that you’d take down a rival, or a BBS, by calling it and connecting a Tesla coil to blow up their modem. Modems weren’t cheap then–pretty much at any point in time from 1985 to about 1998, the cheapest modem worth having cost about $100, and a really good modem in the 1980s could cost considerably more–so nobody took any chances.

Tesla Coil

This is a Tesla Coil. The one I saw in 1992 was bigger than this one appears to be. I can’t imagine any parent letting their son connect this to the household phone line.

The rumors ran rampant. Depending on who you asked, a Tesla coil would blow up a modem, kill a hapless human being who happened to pick up the phone, or even take down service to the entire phone exchange. Those were the rumors I heard–this text file may not be the one I saw at the time, but it runs along the same lines.

What I know for a fact was that sysops considered it rude to mention Tesla coils, and bringing them up was a good way to get yourself blacklisted. Running a BBS was an expensive hobby–you had to dedicate a computer, a modem, and a phone line to it, so you were doing well to get into the game for much less than $500 up front, plus the cost of the software, plus the monthly expense of a phone line. So sysops didn’t take kindly to threats against their equipment.

One BBS I frequented got so sick of the threats that it changed its logon graphic to a Commodore ASCII representation of a police car, with a stern warning. The authorities didn’t really know what to do with these kinds of kids, and some of them ended up in a mysterious place called Charter Hospital.

The first time I actually saw a Tesla coil was in 1992. A classmate introduced me to this eccentric guy who was a disciple of the UFO nut George Adamski. He had a weird device sitting on his dining room table. I looked at it, looked at him, and probably looked confused. “That’s a Tesla coil,” he said, grinning. “I like science.” I didn’t ask for a demonstration. But, having seen a Tesla coil, I know that actually building one was beyond the means of any of the 14-year-olds who would have had the greatest desire to try to use one. And besides that, I don’t think they would have been able to connect a device that resembled the giant five-foot offspring of a spark plug and an electromagnet to a telephone jack without their parents noticing and putting an end to the experiment.

If anyone ever tried that and got caught, I would love to hear the story of how they tried to explain what they were doing.

Rob and I grew up in the same era and saw a lot of the same things, albeit from two different states along Interstate 44. It’s always fun to hear his perspective on those days, way back when. He said at the end of his podcast that it was an exciting time, and he was glad to have lived through it and seen it, and I agree.

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2 thoughts on “Rob O’Hara on phreaking, Tesla coils and modems”

  1. I didn’t mention this on the podcast, but a friend of mine once called me for help after his computer wouldn’t turn on the day after a thunderstorm. This was in 1995 or 1996. He had even turned his computer off before the storm, but the next day his machine wouldn’t boot. I went over and, sure enough, the machine wouldn’t boot up.

    After removing the case I discovered that the back half of his internal modem was completely black. Apparently lightning had hit the building and traveled through the phone line into his modem. Once I removed the modem, the machine booted fine.

    So while I have no doubt, I’m not quite sure just how far voltage like that would travel, or how one would “route” it. Logically in my head, it seems like hooking up a Tesla coil to your phone line would (a) destroy your phone line and (b) blow up the nearest switch box and stop there. I would think it would stop at the first semblance of a fuse or capacitor it came to along the way… ?

    1. Ah, yes, the old modem-fried-by-lightning problem. Somehow I always escaped that, but I knew lots of people who lost modems that way, though never to that extreme extent. No failed boots, no charring–just a modem that wouldn’t work anymore.

      I agree, now that you brought it up, that actually getting the voltage to your target would likely be an issue. I would expect the phone line to be able to handle the voltage, for the same reason that the wiring can survive a lightning strike, but the same thing that protects the central office from lightning strikes would likely dissipate the voltage from the Tesla coil long before it reached the intended target.

      And if it didn’t, the voltage would have to make it through the central office, which in the 1980s was probably full of relays rated for 75-150 volts. So the relay would cook, and that would be the end of the attack.

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