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BBC News - The concrete blocks that once protected Britain

BBC News - The concrete blocks that once protected Britain
http://www.bbc.co.uk/news/in-pictures-46348917
http://www.bbc.co.uk/news/in-pictures-46348917
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  1. Laurent TruilletJanuary 7, 2019 at 1:59 AM

    Very interesting, John !
    I didn't know about this technology.

    ReplyDelete
  2. Laurent TruilletJanuary 7, 2019 at 2:07 AM

    I guess a microphone must have been positioned at the focal point of the mirrors. If all the microphones were connected to one computer, the latter could have calculated the direction of travel of the sound source by computing the evolution of the phase between the microphones.
    Why not try again, now that we have the computers...

    ReplyDelete
  3. LittleJohn MDJanuary 7, 2019 at 4:08 AM

    Listening ears and we have them dotted all over where I live in Kent đź‘Ť

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  4. John TJanuary 7, 2019 at 2:15 PM

    Laurent Truillet yes a microphone was positioned on a metal post in front of them, I think there is a photo of one in Yorkshire here. Not sure what happened next, presumably someone was listening or recording and radioing it up to command.

    ReplyDelete
  5. Margaret Siemers (Siemers Rafter Room)January 14, 2019 at 9:20 PM

    So cool, I love this kind of history!

    ReplyDelete

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