Here's the scenario that blocks more Teams migrations than any other: your enterprise is ready to move to Teams Phone. The desktop phones are easy — they're going away, replaced by Teams clients. The users are easy — they already have Teams. But then someone asks: "What about the elevator phones?"
And the warehouse paging system. And the fax machine in accounting. And the door intercom at the loading dock. And the emergency phone in the parking garage.
These analog devices have been running for years — sometimes decades — on copper lines connected to your PBX. They don't have SIP. They don't have Ethernet. They have two copper wires and a dial tone. And cloud-only solutions like Microsoft Calling Plans and Operator Connect have no way to connect them.
This is the integration guide for the devices that everyone else leaves behind.
The Analog Device Problem in Teams Migrations
Microsoft Teams Phone is a cloud-based SIP platform. It speaks SIP over TCP/TLS for signaling and SRTP over UDP for media. Analog devices speak analog electrical signals over copper wire. There is no direct translation.
The cloud-only options — Calling Plans and Operator Connect — don't address this because they don't give you an SBC. Without an SBC, there's no place to connect an analog gateway.
Direct Routing solves this. Your SBC is the bridge — it handles SIP on the Teams side and can connect to Analog Telephony Adapters (ATAs) on the analog side. The ATA converts analog electrical signals to SIP, and the SBC routes those SIP calls into Teams.
The Solution: ATA + SBC
Analog Telephony Adapter (ATA). An ATA is a small device that converts analog voice signals to digital SIP. It has one or more analog FXS ports (RJ-11, the same connector as a phone jack) on one side and an Ethernet port on the other. You connect the analog device (fax, elevator phone, paging amplifier) to the ATA's FXS port, and the ATA connects to your network via Ethernet.
The ATA registers to your SBC as a SIP endpoint. When the analog device goes off-hook, the ATA generates a SIP INVITE and sends it to the SBC. The SBC routes the call to Teams (for internal calls) or to the PSTN (for external calls).
Supported ATAs:
- AudioCodes MP-1xx series (MP-112, MP-114, MP-118, MP-124) — 2, 4, 8, or 24 FXS ports. Designed to work with AudioCodes SBCs. Good analog fax relay (T.38) support.
- Poly (Plantronics) ATA — 2-port ATA, basic but reliable.
- Grandstream HT series — budget-friendly, 2-port, widely used in SMB but suitable for enterprise analog endpoints.
- Ribbon SBC built-in analog ports — some Ribbon SBC appliances have built-in FXS ports, eliminating the need for a separate ATA.
SBC configuration. On the SBC, you configure the ATA as a SIP endpoint with a phone number (DID). You create a voice routing policy that routes calls from that DID through Teams. For inbound calls to the analog device, Teams routes the call to the SBC, which routes it to the ATA, which rings the analog device.
Device-by-Device Integration Guide
Elevator emergency phones. Elevator codes require an emergency phone in every elevator car. These phones must be able to dial 911 (or a monitoring service) without requiring a user to dial a prefix. They're typically analog — connected to a phone line that auto-dials when the handset is lifted.
Integration: Connect the elevator phone to an ATA. Configure the ATA to dial 911 (or the monitoring service number) on off-hook. Route through the SBC to the PSTN. Ensure E911 compliance — the elevator phone's location must be in your E911 location database.
Warehouse and facility paging systems. Paging systems typically use an analog phone line for access — you call a number, get a prompt, and page over the speakers. Some modern systems support SIP natively; many older ones are analog.
Integration: Connect the paging system's analog line to an ATA. Assign a DID. Users call the DID from Teams to trigger a page. Configure the SBC to route the DID to the paging system.
Fax machines. Fax is still alive in healthcare, legal, and manufacturing — and it's surprisingly hard to kill. Fax machines don't work well over standard VoIP because fax tones are sensitive to jitter and packet loss.
Integration: Connect the fax machine to an ATA that supports T.38 fax relay (a protocol designed for fax over IP). AudioCodes ATAs have strong T.38 support. Configure the SBC to use T.38 for fax calls. This is the most reliable way to maintain fax functionality in a Teams environment.
Door entry / intercom systems. Door intercoms that use analog phone lines for communication can be integrated the same way — ATA + SBC. The intercom gets a DID, and users can answer the door from Teams.
Alarm panel communicators. Some alarm and fire panels use analog phone lines to communicate with monitoring centers. These can be integrated via ATA, but require careful testing — alarm protocols can be sensitive to VoIP timing. Verify with your alarm vendor.
Configuration Overview
The configuration steps for analog integration:
- Provision the ATA. Configure the ATA's network settings (IP, VLAN, QoS) and SIP registration (SBC IP, credentials, codec preferences).
- Configure the SBC analog port. Create a SIP endpoint on the SBC for the ATA. Assign a phone number (DID). Configure call routing for that number.
- Configure voice routing policy in Teams. Add the analog DID to your Teams voice routing policy so calls to/from the analog device route through the SBC.
- Configure E911 for analog devices. Add the analog device's location to your E911 location database. If an elevator phone dials 911, the PSAP must receive the correct dispatchable location.
- Test. Place a test call from the analog device. Place a test call to the analog device. If it's a fax, send and receive a test fax. If it's an elevator phone, verify 911 routing with your PSAP.
Why This Is Our Technical Moat
Analog device integration is the capability that separates specialists from generalists. Most IT consulting firms can configure a Teams Direct Routing SBC for user voice. Very few can integrate analog devices — and fewer still can do it while maintaining E911 compliance for those devices.
This is why enterprises with elevator phones, paging systems, and fax machines can't use Operator Connect or Calling Plans. And it's why those enterprises need a specialist for their Teams migration — not a generalist.
If you have analog devices and you're evaluating migration paths, ask any prospective vendor one question: "What happens to our elevator phones?" If the answer is anything other than "We integrate them through an ATA on your SBC," keep looking.
Get your analog integration assessment — we'll audit your analog infrastructure and map the integration path into Teams Direct Routing.