"POTS replacement" is often shorthand for "put in a cellular communicator," but the right answer depends on which line is being replaced and what the building needs it to do. Here is a clear comparison of the three viable paths.
Option 1: Cellular communicator (LTE-M)
Best for: Fire alarm dialers, standalone intrusion, elevator phones (via purpose-built cellular elevator phone hardware).
How it works: A UL 864 Listed cellular communicator replaces the two POTS lines on the fire alarm panel. Signals go over LTE-M cellular to the UL-Listed central station. Path is supervised on a 60-second or better polling interval. Dual-carrier options (AT&T + Verizon) are available for higher-availability sites.
Pros: Fastest to install (typically half a day). No dependency on building IT. Predictable monthly cost. UL-Listed and code-compliant on its own.
Cons: Requires adequate cellular signal at the panel location. Sites in basements, deep interiors, or shielded electrical rooms may need an external antenna.
Option 2: Dual-path IP + cellular
Best for: High-value, high-occupancy, and mission-critical fire alarm.
How it works: Primary path over the building's internet (typically Ethernet from the panel to the network), backup path over LTE-M cellular. Both paths are supervised. Failover is automatic and typically invisible to the central station.
Pros: Fastest signal delivery, highest availability, aligns with the NFPA 72 direction for current best practice, often cheaper monthly than dual cellular.
Cons: Requires a dedicated network drop and coordination with building IT for VLAN placement. Panel firmware and communicator must be compatible with the network configuration.
Option 3: Managed facility voice network (MFVN)
Best for: Sites with many POTS-era devices (alarm, elevator, fax, modem) where a coordinated single-carrier managed service simplifies the migration.
How it works: A carrier delivers a managed IP voice service that appears to end devices as a POTS line — same connector, same behavior, same supervision. The carrier owns the last-mile transport, backup, and quality.
Pros: Minimizes end-device replacement. Handles many lines under one contract. Explicitly recognized in current NFPA 72 language.
Cons: Availability varies by market. Monthly cost is often higher than pure cellular. Locks you into a specific carrier and their service quality.
What to pick, by scenario
- Single small commercial with a fire alarm dialer and one elevator: Cellular fire alarm communicator, cellular elevator phone. Done.
- Mid-size office or multifamily with fire alarm, three elevators, and intrusion: Dual-path IP + cellular fire alarm, cellular elevator phone service (one contract, three cabs), cellular intrusion communicator.
- High-rise or healthcare with dozens of legacy POTS lines: MFVN as the primary path for anything that talks like POTS, cellular backup for life-safety.
- Data center, biotech, or mission-critical facility: Dual-path IP + dual-carrier LTE-M fire alarm, cellular elevator phone, redundant carrier for critical monitored equipment.
What not to do
Do not plug consumer VoIP into a fire alarm or elevator phone. It is neither UL-Listed nor code-compliant. Do not wait for the copper to be cut before planning. Do not migrate fire alarm without also migrating elevator phones and any monitored ancillary equipment — you will end up doing three separate projects instead of one.
The right POTS replacement is rarely the cheapest single line item. It is the one that consolidates supervision, monitoring, and billing under a coherent design that survives the next code cycle.