2659: Optical Telegraph Mar 29, 2022

Before the advent of radio, and even the electric telegraph, there was still a need to transmit specific messages short-distance, especially without the use of cables. This was particularly needed with ships, and while a lighthouse can be useful sometimes, another machine called the optical telegraph was invented. At night, a so-called shutter telegraph use panels to precisely block light in order to transmit a message in code, but during the day, semaphore telegraphs would use long mechanical arms to indicate the different letters. Some could be used to transmit messages up to 20 miles with a telescope and good weather conditions, not only to ships but to other relaying post towers. These machines were not in use very long, but they did inspire the use of other developments that followed shortly.