POTS to VoIP
Carriers are retiring copper and the quotes make it look like a phone swap. It is not. The desk phones are the easy part — what catches people out is everything else that was quietly sharing those lines: the elevator, the fire panel, the alarm dialer, the fax that a regulator still expects to work. This is the survey to do before the cutover date, and what each of those lines actually needs instead.
Doing it
The survey, in the order that keeps the life-safety items from being discovered last. Each step is a thing that has its own owner, its own lead time, and its own way of going wrong.
- Butt set or lineman's handset
- Toner and probe
- Tone generator for line identification
- 01
Inventory every line, not every phone
Get the carrier's circuit list and walk the building against it. The count almost never matches. Lines that appear on a bill and nowhere on a desk are the ones that matter — they are feeding equipment, and equipment does not complain until the day it needs to dial out.
CautionA line with no dial tone today may still be a monitored circuit. Do not mark it dead until you know what is on the far end.
- 02
Find the elevator line and treat it as immovable
Elevator emergency phones are required to reach a monitored answering point, and in most jurisdictions the line has to survive a building power failure. A standard VoIP ATA on a desk UPS does not satisfy that. This is a conversation with the elevator maintenance company and the AHJ before it is a telecom decision.
CautionCutting an elevator line without a compliant replacement can take the car out of service. Confirm the replacement is accepted before the copper is disconnected.
- 03
Identify the fire alarm communicator
Older panels dial out over two POTS lines. Modern practice replaces them with a cellular or IP communicator listed for fire use — not with a generic ATA. The panel's monitoring company has to be involved, the change usually needs to be recorded, and in many places it needs an inspection afterwards.
CautionA fire panel that cannot report is a life-safety fault, not an inconvenience. Never cut this line to see what happens.
- 04
Chase the alarm, gate, and pump lines
Burglar alarm dialers, gate intercoms, sprinkler tamper and flow switches, sump and generator autodialers, and building automation modems all sit on copper in older stock. Each one either gets a listed IP or cellular path or stays on a retained line.
- 05
Decide what happens to fax and card readers
Fax over VoIP works or does not depending on the codec and the far end. If the fax is genuinely required — some medical and legal workflows still are — either keep one analogue line or move to a fax service with a real number. Old card terminals dialing out are the same problem and usually the cheaper fix is a network terminal.
- 06
Check power, then test before you cut
Copper carried its own power. Everything replacing it needs an outlet, and the switch feeding a PoE phone needs to be on a UPS or the phones die with the lights. Stage the SIP service alongside the copper, port a test number, and place real calls — including to the alarm receiver and the elevator answering point — before the disconnect date.
CautionBook the copper disconnect after the cutover is proven, not on the same day. A carrier disconnect is far harder to reverse than a delay.
- Can I just put an ATA on the elevator phone line?
- Usually not, and it is not a telecom judgement to make alone. Elevator emergency communication generally has to work during a building power failure and reach a monitored answering point. A generic ATA plugged into a desk outlet fails both tests. Involve the elevator maintenance company and the authority having jurisdiction, and get the replacement accepted before the copper goes.
- What about the fire alarm panel?
- It needs a communicator listed for fire alarm use — cellular or IP — installed and registered with the monitoring company, not a consumer ATA. Depending on where you are the change may need to be recorded with the AHJ and re-inspected. Treat the panel as the first item on the survey, not the last.
- Does fax work over VoIP?
- Sometimes, and unpredictably. T.38 helps, G.711 pass-through sometimes works, and both depend on the far end and the network in between. If the fax genuinely has to work, keep one analogue line or move to a fax service. Do not discover this on the day.
- How do I find what a mystery line is connected to?
- Tone it. Put a tone on the pair at the block and trace it with a probe — that is what tells you it terminates at the sprinkler riser rather than on somebody's desk. Our toning and tracing guide covers the method, including how to work a live pair safely.
- Will the phones work in a power cut?
- Only if you plan for it. A copper line drew power from the exchange, which is why the phone in the closet still worked when the building was dark. IP phones need the switch, the router, and the internet circuit all to be on battery. Size the UPS for the whole path, not just the handset.
The rest of the section
- 01RJ45 Wiring: T568A and T568BBoth colour codes, pin by pin, side by side.
- 02RJ11 Wiring and Phone PinoutsSix positions, three lines, two colour systems.
- 03Keystone Jack TerminationStrip, seat, punch, snap — without failing the certification.
- 0466 Block WiringFifty rows, four columns, and where the bridging clips go.
- 05110 Block WiringLay the pairs in, press the connecting block on.
- 06Cat5e vs Cat6 vs Cat6a vs Cat8Speed, distance, and power decide it — not the bigger number.
- 07Fibre Types, Connectors and PolishRead the jacket, read the connector, don't mate blue to green.
- 08Subnetting, ExplainedWhere the numbers come from, and the meaning behind them.
- 09PoE Standards and Why It Won't PowerThe switch reserves the class, not the draw.
- 10Camera Lens, Field of View and Pixel DensityCovering the room is not the same as identifying a face in it.
- 11Patch Panels and Labelling to TIA-606A label that survives is worth more than a tidy rack.
- 12Rack Planning: Units, Depth, Weight and HeatIt fits vertically. That was never the hard part.
- 13Writing a Switch ConfigurationFrom factory default to a switch you would hand over.
- 14Networking and Cabling GlossaryThe terms, and what they mean on a job.
- 15Testing an Analogue Phone LineTip, ring, and the four numbers that tell you whose fault it is.
- 16Toning and Tracing a CableFinding one pair in a bundle of two hundred.
- 17Reading a Cable Certifier ReportWhat PASS* actually means, and which number to look at first.
- 18Which Cable Tester Do You Need?Three tiers, and the one most people actually need.
- 19Running an Office Floor RestackEveryone sits down Monday and their machine works.
- 20Cable Management for Desks and RacksTidy is a by-product. Serviceable is the point.
- 21Asset Tagging and CMDB AuditsThe scan is easy. Scanning it into the right record is the job.
- 22Cabling an Office Fit-OutHow many drops, run where, and what it takes to add one later.
- 23Parcel Locker Site SurveysWhether the unit fits, powers, connects — and gets in the door.
- 24VLANs and TrunkingAccess, trunk, tagged, native — and which one is the security hole.
- 25Spanning Tree and Switching LoopsWhy one patch cord can take a whole floor down in seconds.
- 26Reading a TracerouteWhich loss is real, and whose network it is in.
- 27DHCP, DNS and Helper AddressesWhy the new VLAN gets no addresses, and why it is always DNS.
- 28Wi-Fi Channel Planning and AP PlacementMore access points at lower power, not fewer at maximum.
- 29SMART Attributes That Predict FailureA drive can report PASSED while it is visibly dying.
- 30BitLocker: Keys, Recovery and EscrowThe key exists somewhere, or the data does not.
- 31Grounding and Bonding a Telecom RoomOne ground, one path, and no loops between rooms.
- 32UPS Sizing: VA, Watts and RuntimeThe number on the box is not the number you need.
- 33Mounting Displays on Any WallFind the structure. Everything else is a repair bill.
- 34Mounting IP CamerasHeight, angle, and the surfaces that ruin the picture at night.
We do this work
as well as document it
Anyone holding a carrier letter with a copper retirement date on it, trying to work out what is actually connected before the dial tone goes away.