Your Phone Line Is Changing. Make Sure Your Alarm Still Calls for Help.

By MarKeith McDonald, owner of Nuvii Smart Home · Indiana alarm license LAC-000541 · Published October 20, 2026 · Updated October 21, 2026

What's happening

• Federal regulators have allowed AT&T to wind down most of its copper phone network in 18 states, including Indiana.
• AT&T expects the change to be finished by the end of 2029. It's happening area by area, so neighbors may be switched at different times.
• AT&T says it will contact affected customers several times, by letter, email, text and phone, before moving them to newer phone service.

Why it matters for your alarm

Many older alarm systems call the monitoring center through the home phone line. When that line changes, your alarm needs a closer look.

AT&T says its replacement phone service works with alarm systems. But many alarm companies recommend a direct cellular connection instead. A phone company's replacement box isn't something your alarm company can service, or check that it's working.

Here's what matters most: if your alarm can't reach the monitoring center, it may still beep inside your home, but nobody gets the call.

How alarm systems send signals today

A monitored alarm only protects you if it can reach the monitoring center. Most home systems use one of these paths:

• Copper phone line. The panel dials the monitoring center over a traditional landline. This is the path affected by AT&T's copper retirement.
• Internet phone service (VoIP). Phone service from a cable or internet provider runs through a modem or adapter in your home. Some older alarm panels don't communicate reliably over it, and it stops working when your internet or power is out.
• Cellular communicator. A built-in or add-on cellular radio sends signals over a cell network, with no phone line needed. This is what most alarm companies install today.
• Dual path. Cellular plus internet, so one can back up the other.

What happens during a power or internet outage

Alarm panels normally have a backup battery, so the system keeps running for a while when the power goes out. Your modem, router and any internet phone adapter usually don't, unless they have their own battery backup. That means an alarm that calls out over internet phone service can go silent to the monitoring center at the moment you lose power. A cellular communicator running on the panel's backup battery can keep sending signals. How long depends on the equipment and the condition of the battery, so ask your installer.

We've seen this before: the 3G shutdown

When the major U.S. carriers shut down their 3G networks in 2022, alarm systems with 3G cellular radios had to be upgraded or they stopped reporting. The lesson is the same for landlines: find out which network your alarm depends on before that network changes. If you upgrade, ask which cellular technology the new communicator uses.

How to safely test your alarm's connection

1. Call your monitoring company and ask them to put your account in test mode. Never trigger your alarm to test it without calling first.
2. Arm the system and open a protected door, or follow the test steps the monitoring company gives you.
3. Ask them to confirm they received the signal and how it arrived (phone line, internet or cellular).
4. Ask them to take your account out of test mode, and disarm your system.

If the monitoring center never received the signal, your alarm may only be making noise inside the house. In Indianapolis, false alarms can also lead to fines, so test with the monitoring company on the line. Our local page on alarm permits and false alarms in Indianapolis explains the rules, and our 24/7 alarm monitoring page explains how monitored systems report.

Is your alarm on a landline? Three quick signs

1. A phone cord runs from your alarm panel, or a box near it, into a phone jack.
2. You still pay for a home phone line, mostly "for the alarm."
3. Your keypad sometimes shows a phone-line or communication trouble message.

Not sure? We'll check for free.

Your options

1. Ask your current alarm company about a cellular upgrade. Some offer one, often for a fee or a new contract.
2. Compare it with a brand-new system. Before you pay to upgrade old equipment, see what a new ADT-monitored system with a built-in cellular connection looks like. If you're under contract, our Alarm Rescue Program can help eligible homeowners cover the cost of leaving their current company.
3. Retire the extra phone line. Once your alarm runs on cellular, you may not need the home phone line you kept only for the alarm.

Your free Landline Alarm Check

One visit, no cost and no pressure. We'll:

• Check how your alarm sends emergency signals today.
• Tell you whether it's ready for the phone line change.
• Give you your options in writing, so you can decide on your own time.

Questions homeowners ask

Will AT&T cut off my phone without warning?

AT&T says it will notify affected customers several times before any change.

My home phone is through Xfinity or Spectrum. Does this affect me?

This shutdown is about AT&T's copper lines. But alarms on internet-based phone service have their own weak spot: if your internet goes down, your alarm may not be able to call out. A cellular connection avoids that.

My alarm company says I'm fine. Should I still check?

If they've confirmed your system uses cellular, great. If you're not sure, ask them in writing how your alarm sends its signals.

What does it cost?

The check is free. If you want an upgrade, you'll get an exact price in writing before you decide.

What areas do you serve?

Indianapolis, Carmel, Fishers, Noblesville, Westfield, Zionsville, Greenwood, Avon, Brownsburg, Anderson, Greenfield and Richmond. Nearby? Just ask.

Nuvii Smart Home is an ADT Authorized Dealer and is not affiliated with AT&T or any other company named on this page; all names are trademarks of their owners. Phone line information is based on public reports as of October 2026, and timelines may change. Alarm Rescue Program available to eligible homeowners and requires a new ADT monitoring agreement and credit approval. Indiana alarm license LAC-000541.