The problem began sometime before 7 a.m. and affected calls to seven-digit numbers at the county government center, OES district coordinator Jeff Norris said.
Norris said the phone system includes redundancy components intended to prevent the lines from going down.
"A component failed catastrophically. I can't remember a failure like this," he said.
Some of the lines were restored by about 8:30 a.m., and all phone service was back to normal about an hour later, Norris said.
Technicians continued testing the lines and confirmed at about 10:30 a.m. that they were "stable and secure," Norris said.
The problem did not affect calls to 911, according to Norris.
The cause of the failure remains under investigation.