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

https://www.cryptomuseum.com/covert/opto/jo402/index.htm

by walterbell • 5 years ago

50 14 5 years ago

cryptomuseum.com

bobowzki• 5 years ago

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

mykhamill• 5 years ago

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

verytrivial• 5 years ago

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

ryanmercer• 5 years ago

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.

buescher2• 5 years ago

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.

sigmaprimus3• 5 years ago

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.

jhgb2• 5 years ago

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

Why would they become radioactive?

mkj• 5 years ago

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.

bane• 5 years ago

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

dylan604• 5 years ago

an on/off switch?

buescher2• 5 years ago

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

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

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