MORSE’S MAGNET: In the 1800s, electromagnetism became increasingly important, as in the telegraph, where closing and opening a circuit remotely activated an electromagnet. In this 1837 Samuel Morse demonstration telegraph, a “port-rule” transmitter [foreground] transmits the numbers 1 through 9 to the pen register receiver [rear]. A codebook translated numbers into messages. For example, “8732” might mean “reply requested.”
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