Just as vinyl records have a pattern of grooves and ridges that contain the sound, talking tapes - which were originally developed in 1918 - work on the same principle. Along the length of the tape is a fine pattern of grooves, and when you run your finger nail along the tape, you can 'play' the encoded message.
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Did you know that a single company controls 80% of all glasses and sunglasses brands?
The World's Blackest Material
