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TEAMS PHONE MIGRATION
A friend of mine renovated his kitchen last year. Six months of planning. Picked the cabinets, fussed over the countertop, ordered an German range that cost more than my first car. Day one, the contractor ripped out the old kitchen and installed everything beautifully. Day three, he tried to cook for his family. The range wouldn't ignite.
Nobody had checked the gas line. The old kitchen ran on a small-bore pipe feeding a basic four-burner stove. The new range needed double the capacity. Six weeks waiting for the utility company, a permit, a wall opening, fifteen thousand euros. Then the kitchen worked.
This is what happens to most Teams Phone migrations.
The whole industry talks about Teams Phone migration like it's a phone-number problem. RFPs cover porting, SBC sizing, Direct Routing topology, calling plans, emergency-services compliance. Discovery meetings argue over concurrent call volume, codec preferences, queue overflow rules. The plan looks complete. Then somewhere in week three of cutover, someone walks up to the warehouse door, presses the buzzer, and nothing happens. Or the lift emergency phone fails its monthly compliance test. Or the security desk realises they can't see the camera feed when the front-gate intercom rings.
The phone numbers were the easy part. The peripheral devices, the ones nobody scoped, are the gas line.
What gets planned, every time
Ask any Teams Phone migration team what's on their list and you'll hear the same things. Number porting. Direct Routing or Operator Connect. SBC vendor. Calling Plans budget. Auto-attendants and call queues. Headsets, handsets, conference-room kits. Compliance recording, if you're regulated. E911 mapping. Maybe a parallel run window. Cutover weekend logistics.
This is the visible kitchen. Cabinets, countertops, appliances. All of it gets attention because it lives in the phone-system mental model. It's what the PBX vendor sold you. It's what the Teams partner is comfortable scoping.
What never makes the list
Walk through any building older than five years and you'll find a quiet ecosystem of communication devices that have nothing to do with the phone on a desk. Door intercoms. Video door stations at reception. Paging systems with overhead speakers across a warehouse or production floor. Lift emergency phones, which in most jurisdictions are legally required to both call out and accept inbound calls. Loading-dock buzzers. Gate intercoms in the parking garage. Cleanroom paging. Healthcare nurse-call systems. Conference-room ceiling speakers. Production-floor PA for shift changes. Forklift hands-free comms in the bigger DCs. Visitor kiosks with a "press to call reception" button.
That's a dozen categories before you start counting what's specific to your own building. Each of them is a phone. Each of them used to hang off the PBX. None of them is on the migration plan, because none of them is owned by IT.
That's the gas line.
We call it the Ghost Network. It's been there for years, doing its job, talking to the PBX, invisible to the people now responsible for moving everything to Teams.
Why this keeps happening
Three reasons.
These devices got installed at different times, by different vendors, often years apart. Intercoms came in with a 2014 access-control project. Paging was added in 2018 when the warehouse expanded. Lift phones are part of a building-services contract IT has never seen. The PBX absorbed all of them silently because that's what PBXs did. Nobody at the migration table thinks of them as phones.
Ownership is split. IT owns the phone system. Facilities owns the doors and paging. Building services owns the lifts. Security owns the cameras and the gate. In a typical company those four groups don't sit in the same meeting until something breaks. A proper discovery starts with a building walk alongside the head of facilities. It would surface every one of these devices in twenty minutes. It almost never happens.
The devices are old, reliable, and invisible. They've been working for ten or fifteen years. Nobody touches them, nobody documents them, nobody puts them in the asset register. Out of sight, out of plan.
The day the bill arrives
Here's what missing the gas line looks like in real life.
The lift emergency phone goes silent on cutover Saturday. The building manager doesn't notice until Tuesday's monthly compliance test. The lift now fails inspection. Best case, you have a week to sort it. Worst case, the lift goes out of service in a building with reduced-mobility tenants. Regulated, public failure.
The reception video intercom stops working. Visitors stand outside in the rain. Couriers can't deliver. Someone tapes a phone number to the door and asks people to call. It looks shabby for a month while procurement tries to find a replacement that fits the existing wall mount.
The warehouse paging fails during a near-miss safety incident. The shift supervisor can't reach the floor. The incident report flags the comms failure. Insurance asks questions. Health and safety opens an investigation.
Then comes the cost. Replacing all these devices just to make them speak your new protocol runs five to ten times the cost of integrating what you already have. A new SIP video door station is around €1,200 installed. You've got six of them. That's €7,200 just for the doors. Add paging, lifts, outdoor intercoms, and you're looking at fifty to a hundred thousand euros in unplanned capex. Plus weeks of project delay. Plus the operational pain while it all gets coordinated.
All of that, because the gas line wasn't on the plan.
The "we'll just put a SIP gateway in front" trap
This is the moment someone says "we'll front-end it with a basic SIP gateway and route the calls back into Teams." Sounds reasonable. It's an expensive shortcut.
Basic SIP gateways are audio-only. They terminate the SIP leg, hand audio into the platform, done. No video. No camera feed. No two-way visual confirmation when someone rings the bell. No paging-zone management. No identity flow. You've solved the technical problem of "the call connects" and shipped a worse user experience than the company had before.
A 2014 video door station with a colour camera, where the receptionist used to see who was at the door before deciding to let them in, becomes a beep on someone's headset. They can't see anymore. Multiply that across every intercom in the building and you've quietly downgraded the physical security posture as a side effect of a phone project.
Same story with paging. Basic gateways treat overhead speakers as a single audio destination. Real paging needs zones, priorities, scheduled chimes, emergency override, and the ability to page from a Teams client to the right speaker group without the user having to think about which one. Not a nice-to-have. A core requirement in any building over a certain size.
Basic SIP gateways are the equivalent of running the new Italian range on the old gas line. There's a flame. The kitchen does about a quarter of what it should.
What good looks like
The right version of this is unglamorous. You walk the building before the migration plan is signed off. You list every wall-mounted device that makes a noise or accepts a call. You ask facilities, security, and building services to do the same. Then you map each device to a known integration path inside Teams. The door rings a Teams team with the camera feed visible alongside the call. Paging happens from a Teams client to the correct zone. The lift phone calls out and accepts inbound calls without anyone touching the lift hardware.
No rip and replace. No parallel system that "we'll consolidate in phase two." No quiet downgrade of the physical security stack to make the phone project look on-budget.
The migration plan should match the building. Not the other way around.
Where to start
Before the next vendor meeting, do the walk. One hour. Bring someone from facilities. Note every device. Photograph the labels. You'll find more than you expected, and the list itself will reframe the conversation with whichever partner is doing the migration.
We put together a checklist that covers the twelve peripheral-device categories that nearly always get missed in Teams Phone migrations, with the questions to ask for each one before the project plan locks. It's the document I wish I'd had on every migration we've walked into halfway through.
Ten minutes with your facilities lead. Saves the kind of week that ends in a compliance call.
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