Home Security Systems & Alarms

Bought a House With an Alarm System? Here's What to Do

By the Home Security Systems & Alarms editorial team · Research-based (no hands-on testing) - see how we evaluate · Last updated August 20, 2026

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If your house is brand new rather than second-hand, this is not your page. A builder-installed panel is a different problem: the hardware is current, nobody has lost the codes, and the question is what the builder's package actually contains and who controls the account. Go to what you actually own in a builder-installed alarm system instead.

Almost every real-estate forum has a version of this thread: "New house came with an alarm keypad. It beeps sometimes. No codes, no manual, no idea who installed it. What do I do?" The answer is a short sequence - identify, get control, work out how the thing was supposed to call for help, then choose one of four paths - and none of the steps require paying whoever's sticker is on the box.

First, the ownership question, because the branding is designed to answer it for you

A yard sign and a company logo on the keypad create a strong impression that the previous owner's alarm company still owns something in your walls. In the typical residential case it does not, but the honest version of this answer is more specific than "it's yours".

What settles it is your purchase agreement, not the logo. Hard-wired equipment fastened to the structure is ordinarily treated as a fixture and conveys with the property, which is why almost nobody is asked to hand a panel back at closing. There is also direct evidence from inside the industry: ADT's own Residential Services Contract states that "All equipment installed by ADT pursuant to this Contract shall be owned by the Customer except as otherwise agreed in writing". That is the largest traditional provider in the country saying in its own paperwork that the hardware belongs to the customer by default.

Three exceptions are worth two minutes of checking:

  • Leased or financed equipment on an unpaid account. Some providers finance the equipment across the contract term rather than selling it outright, and some reserve a right to repossess. If the sellers left an account open and unpaid, that is their problem to close, but it is your doorbell somebody may want to collect.
  • The sign and the stickers are genuinely not yours. The same ADT contract states that the yard sign and window decals remain the property of ADT. It is a small thing, but it is the one item on the property that the branding is accurate about, and almost nobody publishes it.
  • Anything "otherwise agreed in writing". That phrase is doing real work in the sentence above. If the sellers signed a different arrangement, the contract they signed governs, and you cannot see it unless you ask them for it.

This is general information rather than legal advice, and the purchase contract for your specific house is the document that actually decides the question. If a company contacts you claiming ownership of equipment in a home you bought, ask them in writing which agreement they are relying on and get the answer before anyone visits.

Step 1: Identify what's on the wall

You're looking for two things: the brand/model of the panel and whether it's currently monitored.

  • The keypad is not the panel. On wired systems (most inherited ones), the brains live in a metal enclosure in a basement, closet, garage, or utility room. The model that matters is on the circuit board inside that box. Common finds: Honeywell/Ademco Vista series, DSC PowerSeries, and company-branded versions of the same - ADT's Safewatch Pro 3000, for instance, is a rebranded Honeywell Vista-20P (our ADT equipment guide decodes that family). All-in-one wireless keypads (the panel is the keypad) are the other common case.
  • Ask the humans first. The previous owners - via your agent if needed - can often hand you the master code, the manual, and the installing company's name in one email. This single step regularly saves hours. Ask specifically: master code, monitoring company (if any), and whether any contract is active.
  • Check monitoring status. If the sellers were paying for monitoring, their service was almost certainly cancelled or will lapse - contracts don't transfer to you automatically. If a company's sticker has a phone number, you can call and ask whether the address has active service; you're not obligated to buy anything.
  • Note what else is wired in. Some installs run smoke/heat detectors or water sensors through the alarm panel. Don't yank power to a panel until you know whether it's also your fire notification - this is the one genuinely consequential mistake in this process.

If it's beeping: work through our guide to a beeping alarm panel for the documented silence-and-diagnose sequence on your panel family. In short, a trouble beep is almost always a dead backup battery (a small sealed 12V unit inside the enclosure, typically $15–$30 to replace - verify for your model) or a failed communication check from a system still trying to phone a monitoring center that stopped listening years ago. Both are fixable; neither means the system is broken.

Step 2: The code problem

Alarm panels have (at least) two important codes: the master/user code that arms and disarms, and the installer code that unlocks programming. Inherited systems commonly lack both. Your escalation ladder:

  1. Try the defaults. A remarkable number of panels were never changed from factory defaults. On Honeywell/Ademco panels the default installer code is 4112 and the default master code is 1234; other brands' defaults are equally well documented in their manuals and on monitoring-company support sites (Alarm Grid publishes a Honeywell code cheatsheet, for example).
  2. Use the backdoor, where one exists. Honeywell Vista panels have a documented backdoor: power the panel fully down (transformer and battery), power it back up, and hold the * and # keys within about 50 seconds to enter programming, from which the installer code can be reset. It works with standard 6150/6160-style keypads but not with touchscreen keypads, and some panels - Honeywell's Lyric, notably - have no backdoor at all. Search "[your panel model] reset installer code" for the exact procedure before improvising.
  3. Know when you're locked out by design. Some installing companies deliberately lock panels with a custom installer code and enable programming lockout. If the backdoor doesn't work, any takeover monitoring company or local alarm tech can advise whether your model can be defaulted - or whether that's the moment to stop sinking time into old hardware.

One caution: only do any of this to a system in a home you own. The procedures are public precisely because legitimate owners get locked out constantly, but on someone else's system this is tampering.

Step 3: Work out how the panel was supposed to call for help, because it probably can't any more

This is the step that changes the price of everything below it, and it is the one nobody volunteers. Every quote you are about to receive contains a piece of hardware whose necessity is never explained, and the reason sits in a national infrastructure change rather than in anything wrong with your house.

Older residential panels were built to report by dialing a telephone line. That is what the pair of thin wires leaving the metal enclosure is for. When the panel trips, it seizes the line, dials a monitoring center and sends a short burst of tones. It is a design from the era when every house had a copper phone line, and for most of the installed base it worked without anyone thinking about it.

That line has largely gone. The FCC's own consumer guidance on the technology transition, reviewed March 2026, reports that 5% of households in the United States have legacy copper telephone service, that 79% of all fixed home voice connections are VoIP, and that 76% of adults live in wireless-only households. The same page tells consumers to check with manufacturers and service providers whether their devices are compatible with a new network, and it names "Security and alarm systems" explicitly in that list alongside medical alert systems and credit card machines.

So the most likely explanation for an inherited panel that powers up, arms, and appears healthy while nothing ever happens is not a fault. It is that the panel is dialing a number down a line that was disconnected or converted to VoIP years ago, and no one has been listening since. The panel will still sound its own siren locally. Nothing it dials reaches anybody.

Why this matters before you take a quote: a takeover company is not being evasive when its quote includes a communicator. It is solving a real problem. But knowing the problem exists is what lets you ask what the part is, what it costs, whether it is yours at the end, and what happens to it if you cancel.

What a communicator actually does

A cellular communicator is a small board that connects to the panel's existing telephone dialer output. Rather than replacing the panel, it presents the panel with what looks like a phone line, captures the data the panel dials, and forwards it over a mobile network. The industry term is dial capture, and it is the reason these devices work across brands.

Two manufacturers' own published descriptions, which are worth reading because they set expectations better than a sales call does:

Device (manufacturer's own page)What the manufacturer statesWhat that means for an inherited panel
Telguard TG-1 Express Certified for AT&T and Verizon LTE, falls back to 3G/4G where LTE is unavailable. "Supports virtually all alarm formats using dial capture for universal panel compatibility." Designed "to use the power and backup battery that already exists in the alarm panel". Meets UL Residential Primary listing requirements for combined burglary and fire. Brand of panel is largely irrelevant. It draws power from the panel you already have, so there is no second power supply or second battery to maintain. The UL Residential Primary listing is the detail to care about if the panel also carries your smoke detectors.
Alula BAT-Mini Dual SIM plus Wi-Fi giving "three reliable, redundant paths"; AT&T and Verizon LTE-M in one radio; "Universal panel compatibility - Dial Capture interface, supporting Ademco Contact ID"; keybus integration for select panels. Described as "designed for Professional Security Dealers and Integrators". Redundant paths matter because a single carrier's coverage at your panel's location in a basement is not guaranteed. Keybus integration, where your panel supports it, is what enables phone arming and disarming rather than signals only.

The part that explains why you cannot just buy one

These are dealer products, and the manufacturers say so on their own websites. Alula describes the BAT-Mini as designed for professional security dealers and integrators, and its site routes homeowners to a "Find An Alula Dealer" page rather than to a purchase path. Telguard's own site invites visitors to "Become a Dealer". This is the same structural pattern our builder-installed system guide found on the automation platform behind new-build panels: the consumer is not the customer, the installing company is.

The practical consequence is not that you are being cheated. It is that the communicator will almost always arrive as a line item on a monitoring quote rather than as something you shop for, and that comparing takeover quotes means comparing what each one includes rather than comparing monthly rates alone. Ask each company four things:

  • Which communicator, and does it use dial capture or keybus integration on my specific panel?
  • Is the hardware sold to me, leased, or bundled into the monthly rate?
  • If I cancel, does it stay, come out, or stop working?
  • If my panel also handles smoke detection, is the device listed for fire as well as burglary?

The routes that avoid the problem entirely

Not every path runs through a cellular communicator, and it is worth knowing which do not before you accept that a monthly fee is unavoidable.

  • An IP module instead of a radio. On DSC and Honeywell panels an Ethernet module such as the Envisalink reports over your home internet connection rather than a phone line or a cellular radio. It is the basis of the self-monitoring route in the table below, and on those same panels it can also coexist with professionally monitored dispatch. We set that out in detail, with published prices, in our guide to running a security system alongside Home Assistant.
  • Replacing the panel rather than adapting it. If the panel is proprietary, locked, or old enough that no communicator is listed for it, money spent adapting it is money spent on a dead end. Path 4 below exists for exactly that case.
  • Accepting a local-only alarm. A siren that nobody is dispatched to is worth less than a monitored system, but it is not worth nothing, and it costs nothing per month. Decide that deliberately rather than by default.

One honest caveat on the two products above: we have not installed either, and both manufacturers' pages carry older copyright dates, so confirm current model availability, network support and pricing with whoever is quoting you rather than treating the specifications here as an order form.

Step 4: Choose your path

PathTypical cost (July 2026 - verify)Best when
1. Reactivate with the original company$0–$100 upfront; their standard monthly rate, plus whatever term they attach to it. Read on their own sites on August 20, 2026: ADT publishes "36 mo. pro monitoring plan starting at $59.99/mo", Frontpoint $44.99 (Interactive) and $49.99 (Ultimate) on 36-month contracts, Brinks Home "starts at just $29.99/month", and Vivint $24.99 on a 36-month agreement with its three larger packages listed at approximately $47, $52 and $57 a month. Those are floors attached to the smallest bundle each company sells, not quotes - see what the floors do and do not meanYou want zero DIY and the company's terms check out. Get the contract terms before the "free reactivation" visit - see our fine-print guide
2. Takeover by a no-contract monitoring company~$0–$250 one-time hardware; ~$8–$15/moThe panel is Honeywell/DSC-based (including most ADT-branded units). Usually the best value - same wired sensors, a fraction of the monthly cost. The one-time hardware figure is mostly the communicator described in Step 3, so ask which one and whether you own it
3. Convert to self-monitoring~$100–$150 one-time (IP module like Envisalink); $0/moYou're technical, want app alerts without fees, and accept that no one dispatches for you - weigh that honestly via our monitoring guide
4. Retire it and start fresh~$200–$700 for a DIY systemThe panel is proprietary/locked/ancient, or you simply want modern equipment. Wired sensors can sometimes still be adopted by retrofit boards

A useful default: if the panel is a Vista or DSC variant and powers up clean, get a free assessment from a takeover company (GeoArm and Alarm Grid both advertise no-contract monitoring from roughly $8–$10/month as of July 2026) before pricing replacements. If it's proprietary or locked, skip straight to path 4 and choose new equipment with our system-choosing guide.

Step 5: Whatever you choose, close the loop

  • Change every code once you have control - the previous owners, their relatives, and their old alarm company all potentially know the current ones.
  • Confirm the sellers' account is actually closed. Their monitoring agreement is a service contract between them and their provider, and it does not transfer to you by buying the house. But an account left open in their name at your address is a live problem: a monitoring center can still be dispatching to your door on signals nobody at your house sent, and the resulting false-alarm fines are assessed against the property. Ask the sellers for written confirmation of cancellation rather than assuming lapse.
  • Update or file an alarm permit. Many cities require a permit in the current occupant's name for police response, and false-alarm fines land on you now. Our false-alarm fines and permits guide explains how to check your city in minutes.
  • If the leftover kit is a connected camera, doorbell or smart lock, the sellers have to release it, and you cannot do it for them. Ring states plainly that "physically uninstalling a device or deleting the Ring app will not release ownership of a Ring device", and SimpliSafe requires a departing owner to remove all cameras and any smart locks from their account so the next occupant can add them to theirs. This is why an inherited device so often refuses to be claimed: nothing is broken, a step was skipped. If you can still reach the sellers, ask them to do it. We set out what the departing side is supposed to do, and what it costs them, in moving house with a security system.
  • Test it. Arm, trip a door, confirm the siren; if monitored, ask the monitoring center to run a signal test with you on the phone.
  • If you retired it, remove the old yard signs and window decals once nothing behind them works - and recycle the panel's lead-acid battery properly rather than binning it. Taking the hardware off the wall has its own order of operations, including cancelling any permit still open in your name and checking whether the panel is powering your smoke detectors: see how to remove or decommission an old alarm system safely.

Related reading: If the sticker on your inherited system says ADT, our guide to reusing old ADT equipment maps every ADT panel generation to its realistic options. Starting from scratch instead? Begin with how to choose a system without getting upsold.

Sources

The ownership, communication-path and communicator sections below are built from primary documents: the FCC's own consumer guidance, and each manufacturer's own product page. We have not installed or tested any of the hardware named on this page.

Update, August 20, 2026. Option 1 in the table above previously described a reactivated provider's rate as "often $35 to $60 a month for traditional providers", with no source behind it. We checked. No provider publishes that band, and three of the four large providers we read publish a starting rate below its lower bound. The row now names each company's published figure with the date it was read, and says plainly that a published floor belongs to the smallest bundle a company sells rather than to a comparable system.