Yes — Ohio rule OAC 3701-31 requires an emergency telephone accessible within the pool area.
Ohio requires the emergency telephone to be accessible within the pool area.
Citation: OAC 3701-31
Ohio doesn't specify a distance, so local health departments generally look for a phone that's visibly accessible without leaving the immediate pool area during an emergency.
SouthEast Telephone installs and monitors cellular emergency pool phones nationwide and can help you meet Ohio's requirements.