Optical “telegraphs” or signaling devices have been traced back to ancient times (using torches) and were the fastest systems to convey messages over long distances. These “telegraphs” could have since been in the form of torches, smoke signals and eventually semaphore towers.
Semaphore towers used large blades/paddles to convey messages. These messages were decoded based on the fixed positions of these arms and could transmit signals up to 150 miles in two minutes using multiple towers.