Replacing the phone line on a security alarm
A lot of burglar and intrusion alarms still report to the monitoring center over a copper phone line. When that line goes dead, the panel keeps beeping at the keypad but nobody on the other end hears about a break-in. Most of the time nobody notices until the monitoring company calls about a failed test, or until something actually happens.
Updated October 16, 2026 · Twisted VoIP
How the panel uses the phone line
When an alarm goes off, the panel picks up the phone line, dials the monitoring center and sends a short coded message. Many panels also call in once a day to show they are still working. If the line is gone, those calls fail. Some panels show a trouble light; many just keep trying.
If your alarm company also gets a daily check-in, a missing one is usually the first sign the line has stopped working. Ask them whether they would notice, and how fast.
Two ways to replace the line
| Replace the line | Replace the communicator | |
|---|---|---|
| What changes | A box gives the panel a working phone line over cellular. The panel and its programming stay as they are. | Your alarm company adds a cellular or internet communicator to the panel and reprograms it to use that. |
| Who does it | Your phone provider, with your alarm company testing | Your alarm company |
| Good fit | Sites that also have fax, elevator or other copper lines to replace at the same time | A single alarm with no other copper lines |
Ooma AirDial, which we sell, is the first kind. Ooma lists burglar and intruder alarms among the systems it supports.
Either way the alarm keeps reporting to the same monitoring center. The difference is who owns the equipment and how many lines one box can cover.
Source: Ooma AirDial.
Questions to ask your alarm company first
- Does my monitoring contract require a specific communicator, or will you monitor a replacement line?
- Which phone number does the panel dial, and does it call in daily?
- Is the alarm part of an insurance requirement or a certificate? If so, does the change affect it?
- Can you be on site, or on the phone, for a test after the switch?
Steps to switch
- Find the copper line the panel uses. It is usually on the same bill as your other phone lines, or your alarm company can tell you.
- Check cellular signal where the panel or the replacement box will sit. Metal enclosures and basements are the usual problem spots.
- Install the replacement, either a line replacement such as Ooma AirDial or the alarm company's communicator.
- Test with the monitoring center: an alarm signal, a trouble signal and the daily check-in, and confirm they received each one.
- Cancel the copper line only after the monitoring center confirms the test.
Is your line on a filing?
Questions
Will my alarm keep working if the power goes out?
The panel has its own battery. The replacement needs one too: AirDial's published battery standby is 16 hours, and more with an extra battery. Ask your alarm company how long your panel's own battery lasts.
Do I need a new alarm panel?
Usually not. A line replacement gives the existing panel a working phone line. A new communicator also works with most existing panels. Very old panels are the exception; your alarm company can tell you.
Can I just use my internet connection?
Some alarm communicators report over the internet. The catch is that the alarm then depends on your internet and its power. Cellular, or cellular with internet as a second path, keeps working when the internet is down.
Get a plan for your lines
Tell us what runs on your copper lines. We'll check the filings for your address and tell you what we'd replace each line with. No obligation. Prefer to talk? Call 623-307-5548.
Related guides
General information, not legal or code advice. Requirements depend on your state, your local authority and your equipment.