Opto-electronic voice transceiver for covert infra-red light communication | Hacker News Reader

Opto-electronic voice transceiver for covert infra-red light communication

cryptomuseum.com

50 pointswalterbell14 comments

Reminiscent of http://ronja.twibright.com/about.php , from before wifi was cheap. It's a 10mbit optical link (AUI ethernet!) using bright LEDs and magnifying glasses.

I almost didn't go to the article because light beam communication was a perennial project in electronics magazines - like this one: https://antiqueradio.org/pe0655.htm

The DDR took the concept to a really nice level of execution, though! Interesting that they used an infrared LED as their light source, given that the device is contemperaneous with the commercialization of infrared laser diodes.

Also there are hyperlinks in the article to pages about earlier devices of this kind that are worth checking out.

Laser microphones were projects that also made their rounds through electronics magazines, mostly in the classifieds on the last few pages right next to the sea monkey adds.

These supposedly worked on the principal that peoples voices would create vibrations on window glass and that by shining a laser beam on said window, it was possible to demodulate the observed laser changes back into sound.

I heard rumors that certain 3 letter agencies used more powerful particle beams to penetrate heavy curtains and other sound dampening measures employed in embassies as counter surveillance. As I heard it, the curtains needed to be changed on a regular basis due to them becoming radioactive.

If these devices actually existed and miraculously worked I would be very impressed with the operators that managed to calibrate them, given all the unknown variables presented in the field.

> the curtains needed to be changed on a regular basis due to them becoming radioactive

Why would they become radioactive?

IDK maybe some sort of Xray like beams were used for better penetration? If the stories are even true, it could have been as simple as changing the curtains to remove listening devices or vary the resonant frequencies.

Anything that would make curtains radioactive would almost certainly also kill anyone in the room in fairly short order. So how many people were killed this way?

You seem to be arguing with me about something that I qualified as a rumor but just to button up this thread I did do a bit of research and found the article below.

Here is a snippet from it and I would suggest seeking answers from those who have a greater expertise/knowledge of these devices.

>>>The system used a "horn antenna" to blast a beam of microwave energy at between 30GHz and 100GHz through a building wall: "If people are speaking inside the room, any flimsy surface, such as clothing, will be vibrating.

https://www.theguardian.com/world/2013/aug/22/gchq-warned-la...

I am not saying that the Stasi built a cyclotron across from the west German embassy then used it to bounce sub atomic(Radioactive) particles back to their spectrum analyzers to eavesdrop on western bureaucrats, but then again I'm not saying they didn't.

Kind of reminds me of how tight beam communications are used in The Expanse universe.

There was just something romantic about the tech of the cold war. Now things are mostly a bit of code injected here or hidden there, but the cold war (and even WWII) was this steady stream of curious gadgets and methods of collecting and passing information.

Oh great, now I'm on eBay looking for Minox cameras again ...

What's the method of modulation? I couldn't quite figure that out in the article. Is it just the IR light's amplitude?

an on/off switch?

Yes, AM, from some of the links in the article. Probably for backwards compatibility: the video version could carry 5 MHz FM video with an AM audio channel.

https://www.cryptomuseum.com/covert/opto/jo406/index.htm

cryptomuseum.com really is one of the best websites. I'm constantly blown away both by the depth and breadth.

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