A wooden portable tower and three soldiers sent and received messages between troops during the Civil War, the U.S. Signal Corps demonstrated.
One man directed another man waving a white flag emblazoned with a red square. The third watched troop movements with binoculars, said Michael Culp of Kalamazoo, Mich.
When Culp got involved with re-enacting as a hobby, he started as an infantryman, then he joined an artillery group.
"I'm not as young as I used to be," said Culp, 46, a former teacher of first- and second-graders.