Telegraphs Ran on Electric Air in Crazy 1859 Magnetic Storm | Wired Science | Wired.com: "On Sept. 2, 1859, at the telegraph office at No. 31 State Street in Boston at 9:30 a.m., the operators’ lines were overflowing with current, so they unplugged the batteries connected to their machines, and kept working using just the electricity coursing through the air."
Cool. That could be a problem today. This would be very similar to an EMP event or a blackout from a big ice storm, it could take a while to recover from.