Yes — Indiana rule 410 IAC 6-2.1 requires a working telephone within or near the pool area.
Indiana requires a working telephone within the pool area, or accessible nearby, for emergencies.
Citation: 410 IAC 6-2.1
"Working" is doing the heavy lifting in this rule — a disconnected landline or dead cellular unit won't pass inspection. Routine testing, such as a monthly test call, is a good habit for Indiana properties.
SouthEast Telephone installs and monitors cellular emergency pool phones nationwide and can help you meet Indiana's requirements.