What Is a POTS Line and What Happens to Your Fire Alarm When the Copper Goes Away

What Is a POTS Line and What Happens When It Goes Away

This can happen and does. A business switches to a new internet provider, better speeds, lower monthly costs, and they cancel the old cable service. What they don't realize is that the POTS line feeding their fire alarm panel was bundled with that old cable account. The new fiber service doesn't include an analog phone line. The panel goes into trouble. Sometimes the monitoring company catches it within hours.

Two related failure modes to understand: First, if the provider switches to fiber with no analog path at all, the panel registers a telephone line trouble fault. The monitoring company should catch it. Second, if the provider delivers a VoIP service marketed as a phone line, older communicator hardware can have issues. The panel may attempt to dial out and get partial acknowledgment, leaving the building's monitoring status uncertain. The building sits unmonitored.

This isn't a hypothetical. It's the real-world version of what is happening industry-wide as carriers decommission their copper networks. The FCC reports that POTS lines in service across the United States have dropped from 177 million in 2004 to roughly 12 million today. The decommissioning is accelerating. AT&T grandfathered 1,711 wire centers across 19 states, including Florida, in October 2025. Physical shutoffs start in June 2026. Lumen stopped accepting POTS changes in May 2025. If your commercial building still uses a POTS line for fire alarm monitoring, you need to understand what that means before your carrier decides for you.

What Is a POTS Line?

POTS stands for Plain Old Telephone Service. It is the two-wire copper analog phone network that has carried voice calls since the Bell era. The central office powers each POTS line at 48 volts DC, which is why these lines continued working during power outages when everything else went dark. That reliability is exactly why life-safety systems were built to depend on them. Fire alarm panels, elevator emergency phones, security dialers, and gate intercoms were all designed around the assumption that a POTS line would always be there.

For most businesses, a POTS line is a line item on a phone bill nobody has thought about in years. Until recently it ran $30 to $60 per month. The FCC removed POTS pricing protections in 2022, and carriers have used that freedom aggressively. Commercial POTS lines now commonly run $60 to $200 per month each. Some are billed higher. That pricing is not accidental. Carriers are deliberately pricing POTS lines high to push customers off copper and onto fiber. If your fire alarm panel requires two dedicated POTS lines, you are looking at $120 to $400 per month just to maintain the communication path, before you pay a dollar for actual monitoring.

Why Carriers Are Pulling the Copper

The regulatory story matters because it tells you how fast this is moving. In 2019, the FCC removed the obligation for carriers to offer POTS at wholesale rates. In 2022, it deregulated pricing entirely. In March 2025, it reduced the required customer notice from 180 days to 90 days. Then in March 2026, the FCC's Network and Services Modernization Order eliminated the public comment and objection process for copper retirement entirely. The 90-day written notice to the account holder is now the only federal protection remaining.

AT&T's timeline is the one most Florida businesses need to track. As of October 15, 2025, AT&T stopped accepting new POTS orders, additions, moves, or changes across Florida and 18 other states. The first wave of physical wire center decommissioning begins June 30, 2026. AT&T filed notice with the Florida Public Service Commission in March 2025 covering Florida wire center retirements. Lumen/CenturyLink stopped accepting POTS changes across 14 states in May 2025. Verizon is migrating its northeast customers to fiber voice, which, as we will get to, is not the same thing as POTS for fire alarm purposes. AT&T's stated goal is to retire nearly all of its copper network by 2029.

The 90-day notice requirement has a problem worth understanding: the notice goes to the account holder. Not your fire alarm contractor. Not your monitoring company. If the phone bill for that dedicated alarm line goes to a facilities manager who doesn't know what a DACT (Digital Alarm Communicator Transmitter) is, there is a real chance the notice gets filed and forgotten. This pattern played out during the 3G cellular sunset in 2022. AT&T shut down 3G in February and Verizon in December. Fire alarm communicators from the 2015 to 2018 era that hadn't been upgraded went dark overnight. The POTS decommissioning follows the same pattern, just with more regulatory scaffolding stripped away each year.

What Happens to Your Fire Alarm When the POTS Line Dies

Most commercial fire alarm panels include a DACT, a Digital Alarm Communicator Transmitter. The DACT is what actually calls your monitoring station when there is an alarm. It dials two programmed phone numbers in sequence, establishes a handshake with the central station receiver, and sends alarm data as a string of DTMF tones. The whole transmission takes seconds. It is completely dependent on an analog phone line to function.

When a POTS line dies cleanly, most panels generate a telephone line trouble fault. Your monitoring company receives a trouble signal and you know there is a problem. Commercial monitoring companies are generally good at catching this. Some monitoring platforms give contractors live visibility on troubles, supervisories, and alarms across accounts, so a lost communication path shows up in real time. Not every monitoring arrangement works that way, though, and not every fire alarm system in Tampa Bay has that level of oversight behind it. The clean-cutover scenario also assumes the line dies clearly instead of transitioning to something that looks like it is working.

The VoIP Trap: Why Fiber Phone Is Not a Replacement

This is the mistake buildings keep making. A carrier retires the copper line and offers fiber voice as a replacement. Or a business switches internet providers and the new service includes a VoIP phone option. Someone assumes the fire alarm will work the same as before. It will not.

VoIP converts analog audio into digital packets for transmission over the internet. That works fine for voice calls because human conversation tolerates minor packet loss. A DACT talking to a central station receiver is not tolerant at all. The DTMF tones the DACT sends are precise analog signals. When they get packetized, compressed, and decompressed, the tones can get corrupted or dropped. The central station receiver cannot decode them. Digitize Inc. documents that VoIP-based connections drop from roughly 90% alarm signal success on copper to around 30%. NFPA 72 does not permit standard VoIP as a listed fire alarm communication path.

The dangerous part is panel behavior. When a DACT dials over VoIP, it may get partial acknowledgment from the central station, enough for the panel to think the call connected, even if no data transferred cleanly. The trouble indicator stays off. The building owner sees no fault. The monitoring station is not receiving reliable signals. This is how buildings end up unmonitored for months while everything on the panel looks fine. This can happen when a business switches internet providers and doesn't realize the POTS line that was running through their old cable modem is now gone.

There is one compliant exception worth knowing: MFVN, or Managed Facilities-based Voice Network. This is a service where carriers deliver voice over fiber but maintain the electrical characteristics of a traditional analog line, engineered specifically to support DACT signaling. MFVN is NFPA 72-compliant if properly listed. But it is different from a standard VoIP business line, and most businesses have no way to verify whether what their carrier is selling qualifies. Standard Comcast Business Voice and standard Spectrum Business Voice are VoIP, not MFVN.

What Else Breaks When the Copper Goes Away

Fire alarm panels are the life-safety priority, but they are not the only systems affected. Elevator emergency phones are required under ADA and ASME A17.1 to connect to a monitored location. When the POTS line feeding an elevator phone dies, that ADA obligation is immediately violated. It is a common finding during cellular upgrades that the existing elevator phone line was already dead, the building staff had no indication of the failure because the phone gives no visible trouble indicator the way a fire alarm panel does. The ADA violation was already in progress.

Gate and parking intercom systems that use telephone-entry dial-out rely on POTS the same way. Security alarm panels with older dial-up communicators face the same failure mode as fire alarm DACTs. Some healthcare facilities still rely on POTS-connected fax lines for clinical documentation. None of these systems are exempt from the copper retirement. For fax machines, gate intercoms, and similar devices, the carrier conversion to VoIP will often keep things running well enough. The critical exception is DACT-based fire alarm signaling. VoIP and fiber phone are not compliant communication paths for fire alarm monitoring, and the panel may not display a visible fault when the line fails silently.

The Fix: Cellular Fire Alarm Communicators

The cellular communicator is the right answer for almost every commercial fire alarm application. The most common misconception we encounter: building owners assume upgrading the communicator means replacing the entire fire alarm panel. It does not. A cellular communicator installs alongside your existing DACT. It captures the DACT's dial tone output, retransmits the alarm signal over LTE to the monitoring station, and confirms receipt back. The fire alarm panel thinks it is still talking to a phone line. You keep your existing panel, existing zones, and existing programming. The upgrade is a box the size of a paperback book, not a panel replacement.

For Silent Knight, Honeywell, and most panels common in the Tampa Bay market, the Napco StarLink is our go-to communicator. The current flagship is the StarLink MAX2, which supports multiple communication configurations including Dual Path Cell (AT&T and Verizon SIMs with automatic failover between carriers) and Dual Path Cell + IP (one cellular network plus local Ethernet). It is panel-powered with no separate power supply required and carries UL 864 10th Edition listing. It won the 2024 ESX Innovation Award.

For buildings where carrier coverage is uncertain, the Telguard TG-7FM launched in August 2024 as the first fire alarm communicator with a multi-carrier SIM. It auto-selects the best signal among AT&T, Verizon, and T-Mobile and switches over without dropping the connection. Hardware runs $325 to $390. The DSC LE4010CF-AT is a reliable universal option at around $340 MSRP with its own self-contained power supply. Every one of these installs the same way: wire the communicator's terminals to the DACT output on the panel, route the antenna outside the metal enclosure, program Contact ID format, coordinate account setup with the monitoring station, test, and verify.

What It Actually Costs

In the Tampa Bay market, a straightforward cellular communicator upgrade on an existing commercial panel, hardware, installation, programming, and testing, runs around $400. That is the real number from actual jobs, not a national cost guide estimate.

Most clients are surprised by the monthly math. Two dedicated POTS lines for a fire alarm DACT typically run about $40 per month each at current rates, so $80 per month just for the phone lines before monitoring fees. Cellular communicator monitoring runs in a similar range to what you were already paying for monitoring. The POTS line cost disappears entirely. Fire Systems Inc. analyzed the comparison in 2024 and found most buildings come out neutral to slightly ahead on monthly costs once the POTS line fees are removed. For any building paying $100 to $200 per month in inflated legacy POTS fees, the hardware pays for itself in one to three months.

The cost nobody mentions is the downside scenario. An unmonitored fire alarm at the time of a fire is a coverage issue with your insurance carrier. NFPA 72 noncompliance is an AHJ violation. The conversation with your insurer after a fire where the panel wasn't transmitting is not one you want to have. The $400 upgrade looks simple against that background.

What NFPA 72 and Florida Code Actually Require

Two code facts that most building owners do not know. First: per NFPA 72 Section requirements, the 2013 edition prohibited using two POTS lines as the dual communication path for new fire alarm installs. If your panel is still running primary and backup on two POTS lines, it has been out of compliance with current NFPA 72 for over a decade. The FCC retiring your copper line doesn't create a new code problem. It exposes one that already existed.

Second: NFPA 72's 2022 edition explicitly prohibits POTS as a sole transmission path. Florida adopted the 8th Edition Florida Fire Prevention Code on December 31, 2023, which incorporates NFPA 72 by reference. Under Section 26.6.3.5.1, two independent paths or a single path with 60-minute supervision heartbeats are required. Cellular LTE with UL 864 listed equipment qualifies as a compliant sole path. The direction the code has been moving for over a decade points directly at where we already are: copper is out, cellular and IP are in.

On permits in the Tampa Bay area: in practice, a straightforward cellular communicator swap on an existing panel typically does not require a permit and is treated as a like-for-like component replacement. If your specific AHJ requires notification or a permit, Florida HB 551 (effective July 1, 2025) mandates those permits be issued within two business days with no plans submission required. Work can begin immediately after application. The upgrade process is fast. The only question is whether you do it before your carrier sends the 90-day notice.

The POTS sunset is an active process, not a future concern. AT&T's first Florida wire center shutoffs start June 2026, and the 90-day notice goes to the account holder, not your fire alarm contractor. If your panel still dials over a copper line, the cellular communicator upgrade is a few hours of work and costs around $400. For help confirming whether your fire alarm communication path is still compliant and what the upgrade involves, the TSS USA fire alarm page covers POTS line assessments, cellular communicator upgrades, and NFPA 72 compliance across the Tampa Bay commercial market.