POTS replacement glossary

Phone lines and the copper network

POTS

Plain old telephone service: an analog phone line on a copper pair, powered from the phone company’s central office. Elevator phones, alarm panels and fax machines were designed around it. See the POTS line replacement guide.

Copper retirement

A carrier removing or replacing its copper facilities with fiber or wireless. Under the FCC’s 2026 rules, carriers post public notice of copper retirements but no longer file them with the FCC. See the AT&T copper retirement guide.

Wire center

The building and serving area of a local phone exchange. Carriers file discontinuance applications by wire center, so two buildings in one city can get different dates.

Section 214 discontinuance

FCC authorization a carrier needs under Section 214 of the Communications Act to stop offering a service. Since the FCC’s March 2026 order, every discontinuance application has a 31-day automatic grant period. Details in the AT&T copper retirement guide.

Network change notice

The public notice an incumbent carrier gives before changing its network in a way that affects interconnection, including copper retirement. Carriers post it through industry forums, publications or their website.

Streamlined processing

The faster FCC track for a discontinuance application. Under FCC 26-19, an application qualifies if the carrier certifies that one of five replacement services, such as facilities-based VoIP or mobile wireless, is available throughout the area.

Grandfathering

Keeping a service for existing customers while refusing new orders. It often comes before a full discontinuance.

Carrier of last resort (COLR)

A carrier required by a state to provide basic phone service to anyone in an area who asks. California’s COLR rules are why AT&T’s copper plans there move more slowly.

Demarc

The demarcation point where the carrier’s wiring ends and the building’s wiring begins, usually a block in a basement telecom room. It is where most line inventories start; see the property manager steps.

Ringdown line

A line set up to call one preset number as soon as the device goes off-hook, with no dialing. Elevator phones and call boxes are often configured this way.

Line seizure

An alarm panel’s ability to take over the phone line, cutting off any other phone on it, so the alarm call goes through. It depends on correct wiring to an RJ31X jack.

RJ31X jack

The special jack that connects an alarm panel ahead of other phones on a line, so the panel can seize the line. Keep it in place when the line moves to a new device.

Loop start

The standard signaling method of a residential or business analog line. Replacement devices for alarm panels are expected to behave like a loop start line, per New Jersey’s 2011 fire alarm bulletin.

Replacement technology

POTS in a box

A managed device combining a cellular router, analog phone ports and a battery that replaces copper lines in one room. See POTS in a box explained.

ATA (analog telephone adapter)

A small box that turns a VoIP connection into an analog phone port. It suits plain phones, but regular VoIP is a poor fit for alarms and fax.

FXS port

The analog port on a gateway or ATA that provides dial tone and ring voltage to a phone, fax or alarm panel.

VoIP

Voice over internet protocol: phone calls carried as data. The Minnesota State Fire Marshal says VoIP is not recommended for fire alarm signals because compression affects the data.

LTE

The 4G cellular standard most POTS replacement devices use. Newer devices add 5G.

Dual SIM

Two SIM cards in one device, usually from two carriers, so the device can switch networks. Ask whether both stay active or one waits for the other to fail.

Multipath

Using more than one communication path at the same time, such as cellular plus a wired connection. NFPA 72 has its own rules for how multiple paths are supervised; see fire alarm communicators.

MFVN (managed facilities-based voice network)

A voice service a carrier manages end to end on its own facilities, rather than over the public internet. Fire codes have accepted MFVN paths for alarm dialers when they meet conditions on power, security and testing.

T.38

A standard for sending fax over IP networks by relaying the fax data instead of the audio tones. Ask providers whether they use it and which fax speeds they support.

DTMF

The touch-tone signals a keypad sends. Gate and door entry systems often use them to open the gate, so the new line must pass them cleanly.

Battery backup

The battery that keeps a replacement device running when building power fails. Vendor figures range from about 8 to 48 hours; compare them with code expectations on POTS in a box explained.

Fire alarms and monitoring

DACT

Digital alarm communicator transmitter: the dialer in an alarm panel that seizes a phone line, calls the monitoring company and sends coded tones. See fire alarm communicators.

Supervising station

The facility that receives fire alarm signals from protected buildings and acts on them, such as a central station run by a monitoring company.

AHJ (authority having jurisdiction)

The official or office that enforces the code for your building, often the fire marshal or building department. The AHJ decides whether a new fire alarm path is accepted.

NFPA 72

The National Fire Alarm and Signaling Code from the National Fire Protection Association. Chapter 26 covers how signals reach a supervising station.

UL 864

The UL standard for fire alarm control units and accessories. Some communicators and gateways are listed or certified to it, according to their makers.

CSFM listing

A listing by the California State Fire Marshal that a fire alarm device or accessory is approved for use in California. Ooma and Granite both cite CSFM approvals for their devices.

Contact ID

A widely used format for alarm panels to report events as tones over a phone line. Compressed voice paths can corrupt it, so test it on any new line.

Single communication path

A fire alarm design using one transmission path to the supervising station. North Carolina’s summary of NFPA 72 (2013) says it must be supervised at least every 60 minutes and is allowed unless the AHJ or other rules prohibit it.

Secondary power

Backup power for fire alarm and communications equipment when primary power fails. North Carolina summarizes NFPA 72 (2013) as requiring 24 hours for shared on-premises communications equipment, with an 8-hour exception the authority can approve.

Elevators, refuge areas and 911

ASME A17.1

The Safety Code for Elevators and Escalators. Section 2.27.1 covers the car’s emergency communication; see elevator phone lines.

Elevator line monitoring

A requirement in many A17.1 editions that the emergency phone line be monitored, with a visual and audible signal at the lobby if it fails, as Washington’s elevator program summarizes the 2016 edition.

Two-way communication system

A system that lets a person at an elevator landing or area of refuge talk with a central control point, with audible and visual signals. See emergency call boxes and areas of refuge.

Area of refuge

A protected space where people who cannot use stairs wait for help during an emergency. The IBC requires two-way communication in areas of refuge.

Central control point

The location approved by the fire department that answers two-way communication calls. If it is not constantly attended, the 2018 IBC requires a timed automatic telephone dial-out to a monitoring location or 911.

MLTS (multi-line telephone system)

A phone system that serves many extensions, such as a PBX or hosted system in an office or school. Kari’s Law and RAY BAUM’S Act apply to it.

Kari’s Law

Federal law requiring multi-line telephone systems to allow direct 911 dialing without a prefix and to notify a central location when someone calls 911. See POTS replacement for schools.

RAY BAUM’S Act

Federal law whose Section 506 requires 911 calls, including calls from multi-line systems, to convey a dispatchable location.

Dispatchable location

The street address of a 911 caller plus details such as floor and room. For fixed telephony and fixed VoIP, the FCC lists January 6, 2021 as the compliance date.

E-Rate

The federal program that discounts telecommunications and internet services for schools and libraries. Voice service is not on the FY2026 Eligible Services List; see POTS replacement for schools.

Adequate replacement

The idea that a new service can stand in for a discontinued one. The FCC replaced its old Adequate Replacement Test with a single rule in March 2026, though providers such as Granite still cite results against the old benchmarks.

To compare the costs behind these terms, try the POTS cost calculator.