This uses the ability of LEDs to flash on and off instantly, at millions
of times a second when designed for the purpose, to transmit
information in the same system that semaphore works”
Its strengths are that it cannot be intercepted from outside the walls of the building it is operating in, for the obvious reason light cannot pass through walls. Also, other signals cannot interfere with it—a big issue for Wi-Fi and mobile signals that can collapse altogether when you have enough people on one area—think how bad you signal gets in the middle of an exhibition hall.