[HN Gopher] Opto-electronic voice transceiver for covert infra-r...
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Opto-electronic voice transceiver for covert infra-red light
communication
Author : walterbell
Score : 46 points
Date : 2021-12-20 09:29 UTC (13 hours ago)
(HTM) web link (www.cryptomuseum.com)
(TXT) w3m dump (www.cryptomuseum.com)
| ryanmercer wrote:
| 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.
| buescher wrote:
| 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.
| sigmaprimus wrote:
| 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.
| jhgb wrote:
| > the curtains needed to be changed on a regular basis due to
| them becoming radioactive
|
| Why would they become radioactive?
| sigmaprimus wrote:
| 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.
| jhgb wrote:
| 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?
| verytrivial wrote:
| Oh great, now I'm on eBay looking for Minox cameras again ...
| mykhamill wrote:
| Kind of reminds me of how tight beam communications are used in
| The Expanse universe.
| bobowzki wrote:
| cryptomuseum.com really is one of the best websites. I'm
| constantly blown away both by the depth and breadth.
| bane wrote:
| 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 wrote:
| an on/off switch?
| buescher wrote:
| 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
| mkj wrote:
| 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.
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(page generated 2021-12-20 23:02 UTC)