Since February 16, 2020, federal law has required something simple: anyone on an office phone system has to be able to dial 911 without dialing 9 first. Someone on-site also has to get notified the second that call goes out. It’s called Kari’s Law, and most office managers I talk to have never heard of it. A fair number of older systems in NYC and NJ offices were installed before this rule existed, so it’s worth checking whether yours actually meets it. That doesn’t mean starting over. Most of the time, an older system can be brought up to code with the right add-on or reconfiguration, which is work we do as often as full replacements.
What a Key System Actually Is
You’ve probably used a key system without knowing the name for it. KSU is short for key system unit. A small box controls a handful of outside lines. Each desk phone has buttons that light up so you can see which line is busy. That’s it. No real routing logic behind it, nothing fancy. It’s simple, it’s cheap to install, and it works fine for an office running a few dozen employees or fewer on straightforward calls. It doesn’t do much beyond that. There’s no real call routing logic, no easy way to add features, and expanding past its line capacity usually means replacing the whole unit rather than adding to it.
What a PBX Actually Is
Think of a PBX as a small phone company living inside your building. It routes calls between internal extensions and shares a pool of outside lines, so a 200-person office doesn’t need 200 outside phone lines. That’s how you get auto-attendants, voicemail, and call forwarding between departments.
A PBX scales. It can handle hundreds of extensions without much trouble. But there’s real hardware sitting in a closet somewhere, and growing the system usually means a technician comes out and adds capacity. It’s not as simple as plugging in one more phone.
Where VoIP Changes the Math
VoIP skips dedicated phone lines entirely and rides on your existing internet connection instead. Each call needs about 100 kbps of bandwidth, give or take, which most office internet plans handle without noticing. The bigger shift is financial, not technical. Instead of a big upfront hardware bill, you’re usually looking at a monthly fee per user, often somewhere around $15 to $25 a month. The phones or softphone licenses are the main hardware cost.
Here’s the catch. A phone line on a traditional PBX kept working through an internet outage, because it was never plugged into the internet to begin with. VoIP goes down the moment your internet or power does, unless you’ve planned for backup power and a failover connection ahead of time. That’s not a reason to skip VoIP. Most offices decide the tradeoff is worth it. Just have that conversation before you sign, not after your first outage.
The 911 Requirement You Can’t Design Around
Kari’s Law came with a partner, the RAY BAUM’S Act, which adds one more requirement: a “dispatchable location,” meaning your exact address plus floor and room number. Together, they apply to office phone systems generally, but they bite harder on VoIP than they ever did on a wired PBX.
Think about why. A desk phone on a PBX was physically wired into one room, so the phone company always knew exactly where a 911 call came from. A VoIP extension can follow an employee’s laptop to a different floor, or ring on a mobile app somewhere else entirely. Nobody automatically knows where that call is coming from unless someone configured it correctly. This is exactly the kind of thing that slips through the cracks when a business buys VoIP off a self-service website instead of having someone install and test it properly.
None of this means an older PBX or key system has to be torn out. Being out of compliance is usually a configuration or add-on problem, not a reason to replace working equipment. We check existing systems for this all the time and bring most of them up to code without touching anything else about how they run.
What Actually Decides It for Most Offices We Wire
In practice, the decision usually isn’t “PBX vs. VoIP” in the abstract — it’s what’s already in the walls and what the business actually needs. An office with solid structured cabling and reliable internet is usually a good fit for VoIP, since the backbone is already there. A building without that infrastructure needs the network side addressed first, or a hybrid approach makes more sense while that gets built out. Businesses running fully remote or hybrid teams tend to lean VoIP for the mobile app and softphone flexibility; a business that wants a system that keeps working no matter what the internet is doing that day sometimes still chooses a traditional PBX, budget allowing.
One Disclosure Worth Making Plainly
MetroCom is an installer and systems integrator, not a manufacturer of phone system hardware or software. We design, install, and configure PBX and VoIP systems from established platforms as part of a project, and we handle the structured cabling and network side that either system depends on. We don’t build the phone systems themselves, and our recommendation is based on what your office’s infrastructure and call volume actually need, not on a single platform we’d rather install.
Frequently Asked Questions
Can an existing PBX be upgraded to support VoIP instead of ripping everything out?
Often, yes. A hybrid setup or a gateway can bridge the two, especially if the wiring and network can support it. Whether that’s worth doing over a clean VoIP install depends on how old the current PBX is, and what shape the cabling behind it is in.
Does a small office really need a full PBX, or is a key system enough?
For a handful of employees with simple calling needs, a key system can still be the right call on cost alone. Once you need call routing between departments, voicemail-to-email, or more than a couple dozen users, a PBX or VoIP system earns its cost back in the features it opens up.
Is VoIP call quality actually reliable, or does it sound choppy?
On a properly planned network with adequate bandwidth and correct configuration, VoIP call quality is generally indistinguishable from a traditional line. Quality problems usually trace back to insufficient bandwidth, network congestion, or a system that was never configured for the connection it’s running on, not VoIP as a technology.
What happens to 911 calls if the internet goes down on a VoIP system?
Without a backup plan, a 911 call on VoIP fails the same way any other call does during an outage. Offices serious about this pair VoIP with a cellular failover or a battery-backed connection specifically so 911 and other calls stay live during a network or power interruption.
What This Means for Your Office
If you’re weighing a phone system upgrade, the right starting point is an honest look at your existing wiring and network, not a features list from a vendor. MetroCom’s business telephone system installation covers PBX, VoIP, and hybrid setups end to end, and it’s frequently installed alongside our computer network and structured cabling services since a phone system is only as reliable as the network carrying it.
