POTS in a box: what is inside and where it fits
A POTS-in-a-box unit gives a fax, alarm panel or elevator phone dial tone over cellular or internet once the copper goes. It suits a few lines in a simple building; for a fire panel or a full building, we replace the lines on our own circuit.
What a POTS-in-a-box unit does
A POTS-in-a-box device is a small appliance installed in a building that produces analog dial tone locally and carries the resulting calls over a cellular or internet path. The equipment already wired to the old telephone line plugs into it unchanged: a fax machine, an alarm dialer, a callbox, an elevator phone. The telephone company line is then disconnected.
The same devices are sold as analog line replacement units and as POTS line replacement appliances: one product category under three names. Our guide on what a POTS line is lists the equipment that still depends on analog lines, and four ways to find yours.
POTS IN A BOX® is a registered trademark of DataRemote, Inc. WilloWeb is not affiliated with DataRemote.
Why buildings are replacing their lines now
Copper phone service is going away. AT&T has federal approval to stop it in parts of every Bay Area county from June 1, 2027, and an alarm dialer or elevator phone left on a retired line has nothing to call out on.
Keeping copper is getting more expensive too. Since federal price rules on leased copper lines ended in August 2022, business line rates have gone up, so a line kept only for a fax or an alarm panel costs more than it did.
Three ways to get off an analog line
A box on its own suits some buildings. We supply the other two: replacement lines on a circuit we run, and business VoIP for the whole office.
| Question | A POTS-in-a-box unit on its own | Replacement lines on our circuit | A full move to business VoIP |
|---|---|---|---|
| What it replaces | The copper pair only | The copper lines and the connection under them | The whole phone system |
| Where the call goes | Out over its cellular radio, often the internet too | Over the circuit we run into your building | Over your internet to a hosted platform |
| Who you call when it fails | The unit’s provider, and maybe your internet provider | Us, for the lines and the circuit | Your VoIP provider |
| Best fit | One site, two or three lines, happy with its internet | A fire panel, elevators, or lines nobody has tracked | Replacing staff phones, with a few analog lines left |
| Where it is the wrong answer | Nobody watches its alerts, or nobody owns the fire panel test | The only analog line is one fax | Only the analog devices need fixing |
What it replaces
- A POTS-in-a-box unit on its own
- The copper pair only
- Replacement lines on our circuit
- The copper lines and the connection under them
- A full move to business VoIP
- The whole phone system
Where the call goes
- A POTS-in-a-box unit on its own
- Out over its cellular radio, often the internet too
- Replacement lines on our circuit
- Over the circuit we run into your building
- A full move to business VoIP
- Over your internet to a hosted platform
Who you call when it fails
- A POTS-in-a-box unit on its own
- The unit’s provider, and maybe your internet provider
- Replacement lines on our circuit
- Us, for the lines and the circuit
- A full move to business VoIP
- Your VoIP provider
Best fit
- A POTS-in-a-box unit on its own
- One site, two or three lines, happy with its internet
- Replacement lines on our circuit
- A fire panel, elevators, or lines nobody has tracked
- A full move to business VoIP
- Replacing staff phones, with a few analog lines left
Where it is the wrong answer
- A POTS-in-a-box unit on its own
- Nobody watches its alerts, or nobody owns the fire panel test
- Replacement lines on our circuit
- The only analog line is one fax
- A full move to business VoIP
- Only the analog devices need fixing
Five parts inside most POTS-in-a-box units
Units differ in port count, in whether they can also run over a wired internet connection and in who watches them once they are installed. Most are built from the same five parts.
- Analog ports
- One RJ11 jack for each line the unit carries, and the fax machine or alarm panel plugs into it as it did into the wall jack. Two-, four- and eight-port units are all on the market.
- A cellular radio
- A cellular modem gives the unit a path that does not depend on the building’s network, and many units take two SIM cards so they can switch carriers. Coverage has to be checked at the spot where the unit will hang.
- A battery
- An internal battery keeps the unit working through a building power cut, for a standby time its maker states.
- A management portal
- The unit reports to a web portal that shows whether it is online and can send alerts, for an outage or a low battery, for example. Who watches the portal varies: some providers monitor every unit they have deployed, others leave it to you.
- Dial tone made inside the unit
- The unit generates the dial tone, ringing and line voltage itself, a few feet from your equipment, and sends each call on as data. Dial tone at the jack proves only that the unit has power; a call can still fail when the cellular or internet path is down.
What fire alarm panels and elevator phones ask of the unit
On a fire alarm panel, the unit becomes part of the panel’s path to the monitoring company. Its listing covers the unit; your fire authority approves the system as installed. For a single path, NFPA 72 (2022 ed.) asks for supervision at intervals of no more than 60 minutes, no more than 90 seconds from an alarm at the premises to its display and recording at the supervising station, and at least 24 hours of secondary power for the equipment at the premises that carries the signals; the clauses, and the conditions on them, are set out on our fire alarm panel phone lines page.
Elevator cab phones have their own code requirements, which we cover under elevator phone line requirements.
POTS in a box questions
For as long as its battery lasts, which is a standby time its maker measures under its own test conditions. Size it against what the connected equipment needs. A fire alarm panel keeps its own standby batteries, and the unit carrying the panel’s signals falls under the secondary power requirement in NFPA 72 too: two batteries, two runtimes, each sized for its own load.
One multi-port device can carry several lines, but only the lines that are physically within reach of it. A fax line in the back office and a callbox at the far end of the parking structure are not in the same closet, and running new copper to consolidate them onto one unit can cost more than a second device. A monitored fire alarm panel makes the case for a unit of its own at the panel, since its path, its supervision and its standby power have to be engineered for that panel alone.
Tell them before you order. They need the account number and the site, the date and window so the account can go on test, the reporting format the panel uses and the receiver number it dials, and warning that the calling line identification presented to the receiver may change, because some receivers use it to identify the panel. Then ask for the one thing that matters afterwards: a written confirmation that every signal type the panel can send was received during the test, and that taking the new path down showed up as a failure at their end. Until someone puts that in writing, the cutover is not finished.
The review costs nothing and commits you to nothing. After it you get a quote for your building, line by line. No overage, exchange or option fees apply, and the rate in the quote holds: we do not raise it at the 12- or 18-month mark, or ever. Outside the Bay Area, start with our national POTS line replacement service.
Tell us what is plugged into each line
Send the model number of each device on an analog line, where in the building it sits and who monitors it. With those three answers we can say which of the three approaches suits each line, and the free review confirms it on site.