CHAPTER 14A Manually Operated Sequencer:Invisible Secret Code Display
THE HANDHELD DEVICE DESCRIBED IN THIS CHAPTER’S project allows you to transmit to a friend ten individual coded shapes using a display composed of seven LEDs in a star formation. The key feature of this device is that you can’t see its coded image unless you know how to view it. This is because the display transmits the image using infrared light, which can’t be seen by the human eye. The image can be seen only by viewing it through a digital camera.
Any budding secret agent worth their salt should have one of these devices. Even if your fellow spy is across the room from you, you could still “see” the coded image by using your digital camera to zoom in on their handheld transmitter. ...
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