Twilight settled over the Iron Dragon Gap, blanketing the valley in deep indigo shadows.
Behind the mortal low roof walls, thousands of torches were lit inside deep earthen fire bowls, shielded from sky view by thick canvas baffles. In the comms trenches, teams of signalmen were laying out the nervous system of the mortal army. A extra, distributed relay mesh connecting all one hundred and twenty-eight mirror squads across fifty li of front.
Lin Tao knelt inside the central junction bunker, examining the master sound signal line.
Instead of relying on fragile spiritual magic charms or shouting messengers, Lin Tao had designed a clockwork sound relay using high-pulling copper wire suspended on star-iron insulators. At three-hundred-pace intervals, balanced deep ring diaphragms amplified the sound pulse. It allowed a signal generated at the center to travel the entire five leagues in less than forty split seconds.
“Test line seven,” Lin Tao commanded into the copper speaking horn.
Three hundred paces to the west, a ringing clack echoed back along the wire. It was followed by a second and a third as the chest muscle repeated the signal down the line.
“Line Seven checked,” Lin Tao noted, marking his ledger with spirit chalk. “Sound delay is thirty-eight split seconds. Within acceptable limit.”
