# TTY Machines After Copper: A 90X1 Use Case

> Keep TTY/TDD text telephones working after copper retirement: the 90X1 replaces the POTS line with a G.711 path that carries TTY tones intact. Setup, test, PDF.

- Published: November 5, 2026
- Author: DataRemote
- Topics: Use Cases, Compliance, POTS Replacement, Copper Retirement
- Primary entity: endpoint:tty-machine
- Related entities: family:pots-in-a-box, platform:ara, product:90x1, product:90x2, product:vab-1, solution:pots-line-replacement, solution:analog-telephone-connectivity, endpoint:analog-telephone, endpoint:fax-machine, topic:pots-line-replacement, topic:copper-retirement, topic:legacy-analog-line-migration, standard:fcc-copper-retirement-rules, definition:enhanced-911, definition:fxs, definition:loop-current, definition:analog-telephone-adapter, definition:battery-backup, definition:cellular-pots-replacement
**Direct Answer:**
A TTY (text telephone, or TDD) lets people who are deaf, hard of hearing, or speech-impaired hold a typed conversation over a phone line. TTYs are found at 911 centers, hospitals, government offices, schools, hotels, transit stations, and public phones, and most run on an analog POTS line. TTY characters travel as audio tones that are easily garbled by compressed codecs and poor network audio. When the copper line is retired, the [DataRemote 90X1](https://dataremote.com/pots-in-a-box/90x1) replaces it with a TTY/TRS-capable analog port that carries the call as G.711 audio over 5G/LTE with wired WAN failover. The TTY plugs in as before, the published TTY number stays, and calls to 911, to a 711 relay service, and to other TTYs go through. This post covers how a TTY uses the line, which rules keep that line in scope, what to check before you order, and how to test each machine. The one-page summary is available as a [PDF white paper](https://dataremote.com/documentation/marketing/dataremote-90x1-tty-machines.pdf).

## Key Takeaways

- **Replace the line, not the TTY.** The TTY's Tip/Ring connection moves to a 90X1 FXS port, and the machine, its number, and the staff procedures around it stay the same.
- **TTY tones need an uncompressed path.** Each character is a burst of two audio tones with no error correction. The 90X1 carries the call as G.711 audio with G.168 echo cancellation, so typed characters are not dropped or garbled.
- **911 and 711 are covered.** The 90X1 provides E911 support with geo-location and supports calls through Telecommunications Relay Services, including 711.
- **The obligation is federal and specific.** ADA regulations require direct TTY access to 911, TTYs or equivalent systems at government offices, and accessible telecommunications where businesses offer customers outgoing calls. The line is how those obligations are met.
- **Real-time text did not retire the wired TTY.** The FCC's RTT rules address wireless handsets and networks. A TTY at a desk still needs an analog line that carries its tones.
- **Lines are supervised and battery-backed.** Ara line-status monitoring raises an alert when a TTY line goes down, and an integrated battery rated for up to 48 hours of standby keeps the line live through an outage.

## The use case at a glance

| Detail | This use case |
|---|---|
| **Endpoints** | TTY machines (text telephones, TDDs) on dedicated analog lines, usually with a published TTY number |
| **Where found** | 911 centers, hospitals and clinics, state and local government offices, courts, schools and universities, hotels, transit stations, and public phone locations |
| **Line today** | One analog POTS line per TTY, carrying the machine's tones to another TTY, a 711 relay service, or a 911 center |
| **Product** | DataRemote [90X1](https://dataremote.com/pots-in-a-box/90x1) 5G POTS IN A BOX®, up to eight TTY lines per appliance |
| **Transport** | 5G/LTE as a G.711 voice path, with wired WAN failover where the site has a wired internet connection |
| **Far end** | 911, a 711 relay communications assistant, or another TTY, unchanged |
| **What stays the same** | The TTY, its published number, the people who answer it, and the accessibility procedures built around it |
| **Management** | [Ara](https://dataremote.com/ara): G.711 codec confirmed per line, line-status monitoring, alerts, remote management |

## How a TTY uses its POTS line

A TTY is a keyboard, a small display, and a modem built for the voice telephone network. It makes an ordinary analog call: it goes off-hook, draws [loop current](https://dataremote.com/newsroom/definitions/loop-current), and dials. What happens next is what sets it apart from a telephone. Instead of speech, the line carries text, one character at a time, as short bursts of audio tone.

1. **The TTY places the call** to a published TTY number, to 711 for a relay service, or to 911. The far end answers with a TTY of its own, or a relay communications assistant answers with one on the user's behalf.
2. **Characters go out as tones.** The TTY encodes each keystroke as a short sequence of two audio frequencies, one for a mark and one for a space, at a slow fixed rate. The international framework for this is ITU-T Recommendation [V.18](https://www.itu.int/rec/T-REC-V.18), which covers text telephone modes and is harmonized with the ANSI TIA/EIA-825 text phone standard used in the United States.
3. **The far end decodes and replies.** The receiving TTY turns the tones back into characters on its screen. By convention the typist ends a turn with "GA" (go ahead) and the conversation with "SK" (stop keying), because the call is half duplex: only one side types at a time.
4. **Some calls mix text and voice.** The FCC's [guide to Telecommunications Relay Service](https://www.fcc.gov/consumers/guides/telecommunications-relay-service-trs) describes voice carry over and hearing carry over, where a user speaks on one leg of the call and reads or types on the other. The same line has to carry both cleanly.

### Why a TTY is harder on a line than a voice call

| Property of TTY signaling | What it means for the replacement line |
|---|---|
| **No error correction, no retry** | A distorted tone becomes a different character or no character. The reader sees a wrong letter or a gap, and nothing on either end flags it. |
| **Tones, not speech** | Voice codecs that compress audio are tuned for speech and can smear the tone transitions. The line must carry the audio uncompressed, as G.711. |
| **Half duplex with abrupt turns** | A character can start the instant the line goes quiet. An echo canceller that clips the first milliseconds of a tone loses the character; the line needs echo cancellation that converges without cutting into the signal, which is what G.168 defines. |
| **Low tolerance for timing drift** | Packet loss and jitter on the transport show up directly as dropped or doubled characters, so the voice path's quality is the TTY's quality. |

The result is the same failure mode fax users know: the line passes a voice test and fails the equipment on it. Our guide to [fax, POS, and ATM lines after copper](https://dataremote.com/blog/fax-pos-atm-analog-endpoints-pots-replacement) covers tone-carrying endpoints in general; a TTY is one of the most sensitive of them, because a human is reading the output in real time.

### A failed TTY line looks like a quiet line

A TTY line at a government counter or a hospital admissions desk may go days without a call. When copper is cut over or a replacement line degrades, nothing on the TTY changes: it still powers up, still shows a cursor, and still goes off-hook. The first sign of trouble is a caller who cannot get through, or a relay communications assistant reporting that the text is unreadable. That silent-failure mode is the strongest reason to pair the replacement line with supervision and a scheduled TTY-to-TTY test, not only with a new carrier.

## Why copper retirement reaches the TTY desk

The copper line under a TTY is not being repriced. It is being withdrawn. The FCC's [guidance for government officials on network modernization](https://www.fcc.gov/modernizing-telecommunications-networks-what-government-officials-need-know) explains that carriers are retiring copper and the legacy time-division multiplexing (TDM) switching behind it in favor of IP and wireless service, and that an incumbent carrier owes a non-residential customer at least 180 days' notice before replacing that customer's copper connection with fiber. The same guidance makes the point that matters for an accessibility line: copper landline service typically keeps working through a power outage, and the services that replace it usually need backup power of their own.

Those notices are already arriving. On January 12, 2026, AT&T's application to discontinue legacy POTS in portions of 18 states was deemed granted under the FCC's streamlined process, with discontinuance authorized on or after November 15, 2026; the dated record is in our newsroom: [FCC grants AT&T applications to discontinue POTS in portions of 18 states](https://dataremote.com/newsroom/news/fcc-grants-att-pots-discontinuance-18-states-november-15-2026). Verizon followed with a [Section 214 application covering copper POTS in nine states and D.C.](https://dataremote.com/newsroom/news/verizon-section-214-application-discontinue-copper-pots-nine-states-dc) A TTY line on either carrier's copper has a date attached to it, whether or not the accessibility coordinator who published the TTY number has seen the letter.

### Who is on the other end of the TTY

The population these lines serve is large and growing older. The National Institute on Deafness and Other Communication Disorders reports in its [hearing statistics](https://www.nidcd.nih.gov/health/statistics/quick-statistics-hearing) that about 15 percent of American adults, 37.5 million people, report some trouble hearing, and that disabling hearing loss affects 22 percent of adults aged 65 to 74 and 55 percent of those 75 and older. Many of them use video relay, captioned telephones, or real-time text on a smartphone. The institution they are calling, however, publishes a TTY number because the regulations below ask it to, and because the TTY is the one device that works for a caller who has none of the others.

### Real-time text and the wired TTY

The FCC's [real-time text page](https://www.fcc.gov/real-time-text) records that on December 15, 2016 the Commission adopted rules permitting wireless service providers and handset manufacturers to support real-time text (RTT) in lieu of TTY technology, with RTT defined to be backward compatible with TTYs and rolled out on wireless networks in phases from December 31, 2017 to June 2021. Two things follow for a facilities team. First, the wireless world is moving away from carrying TTY tones, which is one more reason not to trust a generic voice path with them. Second, the transition is about handsets and networks, not about the TTY on a desk. That machine is a wired analog device, and backward compatibility means the network must still carry its tones. The 90X1 gives it the analog line and the uncompressed voice path it needs.

### The rules these lines sit under

None of the rules below says how a TTY call must travel. Each one says the call must get through, which is the property a migration has to prove.

| Setting | What the rule requires, and where it says so |
|---|---|
| **911 centers and other telephone emergency services** | Telephone emergency services, including 911 services, shall provide direct access to individuals who use TDDs and computer modems. Source: [28 CFR 35.162](https://www.ecfr.gov/current/title-28/chapter-I/part-35/subpart-E/section-35.162). |
| **State and local government** | Where a public entity communicates by telephone with applicants and beneficiaries, TTYs or equally effective telecommunications systems shall be used to communicate with individuals who are deaf or hard of hearing or have speech impairments; automated attendants must provide effective real-time communication with TTY and relay users; and relay calls must be answered like any other call. Source: [28 CFR 35.161](https://www.ecfr.gov/current/title-28/chapter-I/part-35/subpart-E/section-35.161). |
| **Hospitals, hotels, and other public accommodations** | A public accommodation that offers customers, clients, patients, or participants the opportunity to make outgoing calls on more than an incidental basis shall make available accessible public telephones, TTYs, or other telecommunications products and systems; automated attendants must support TTY and relay users; relay calls must be answered like any other call. A public accommodation may use relay services in place of a TTY for calls incident to its operations. Source: [28 CFR 36.303(d)](https://www.ecfr.gov/current/title-28/chapter-I/part-36/subpart-C/section-36.303). |
| **PBX operators and VoIP providers** | FCC rules require all telephone companies that operate PBXs to implement three-digit 711 dialing for access to relay services, and providers of interconnected VoIP service must offer 711 dialing. In an emergency, TTY users should call 911 directly rather than placing a relay call through 711. Source: [FCC, 711 for TTY-based Telecommunications Relay Service](https://www.fcc.gov/consumers/guides/711-telecommunications-relay-service). |

Two cautions. The ADA rules set the obligation to communicate, and a TTY is one way to meet it; an institution that has adopted relay services or RTT for some functions may still keep a TTY line for the ones where it is required or expected, such as emergency access. And a published TTY number is a commitment: callers, relay services, and directories have it on file, so the number must move with the line. The requirements that govern emergency communication circuits in buildings more broadly are summarized on our [emergency communication requirements](https://dataremote.com/newsroom/standards/emergency-communication-requirements) page.

## How the 90X1 connects to a TTY

To the TTY, the 90X1 looks like a standard phone line, and its tones are carried without compression. The appliance sits where the copper lines terminate, usually the telecom closet nearest the desk or counter, and the TTY's phone cord plugs into one of the 90X1's eight RJ-11 [FXS](https://dataremote.com/newsroom/definitions/fxs) ports. The call leaves over 5G/LTE as a G.711 voice path. If the site has a wired internet connection on the 90X1's WAN port, it serves as failover.

Three parts of the appliance's behavior deserve a closer look, because they are where a replacement either preserves the TTY's usefulness or breaks it.

### Clean TTY signaling

The 90X1's FXS ports are TTY/TRS-capable, and the appliance carries the call as G.711 audio with G.168 echo cancellation. In practice:

- **G.711** is the uncompressed voice codec of the public telephone network, so the TTY's tones cross the cellular path with the same waveform shape they had on copper, rather than being modeled as speech.
- **G.168 echo cancellation** removes the line echo that would otherwise return the TTY's own tones to it, without clipping the start of a character.
- **The configure step is a check, not a setup.** In Ara, confirm that the line uses the G.711 codec for TTY traffic. No dialing changes, number changes, or TTY settings are involved.

The 90X2 and VAB-1 datasheets list the same TTY/TRS capability, so a site that is standardizing on LTE rather than 5G, or on a plug-and-play appliance for many small locations, has the same path available. Compare the [90X2](https://dataremote.com/pots-in-a-box/90x2) and the [VAB-1](https://dataremote.com/pots-in-a-box/vab-1) before sizing a portfolio.

### 911 and relay ready

A TTY line exists so that someone can reach help or a service, which means two destinations matter more than any other:

- **911.** The 90X1 provides E911 support with geo-location, so an emergency call from the TTY line carries location information. Our definition page on [Enhanced 911](https://dataremote.com/newsroom/definitions/enhanced-911) explains what a replacement line owes the 911 center. Coordinate any 911 test call with the local public safety answering point (PSAP) before placing it; most PSAPs will schedule a TTY test on request.
- **711 relay.** The 90X1 supports calls through Telecommunications Relay Services, including 711. A relay call is a TTY call on the institution's side and a voice call on the other, with a communications assistant in between, so the TTY leg has to be as clean as a direct TTY-to-TTY call.

### Always available

Copper carried its own power from the central office. A replacement line does not, which is why the FCC's note about backup power applies here. The 90X1 keeps the line live from an integrated 18-cell, 15 Ah lithium-ion battery rated for up to 48 hours of standby (actual runtime varies with usage), and its 12 VDC, 3.0 A UPS output can power an approved connected device. When the battery runs low, the appliance sends a battery alert and shuts down gracefully. The TTY itself is the other half of the outage question: many run from a wall adapter and carry an internal battery for a few hours, so check both. Our definition page on [battery backup](https://dataremote.com/newsroom/definitions/battery-backup) covers how to turn a standby rating into a runtime plan.

The 90X1 is managed through [Ara](https://dataremote.com/ara), DataRemote's device management platform. For a TTY deployment, two Ara functions carry the weight: line-status monitoring with alerts, so a TTY line that drops raises an alert instead of waiting for a caller to report it, and remote management, so the codec setting can be confirmed and a line checked without a visit to the desk. Ara watches the line. It does not watch the TTY, so keep a scheduled TTY-to-TTY test on the calendar.

## Before you order: six questions for each TTY line

Most of the work in this migration is in the inventory, not the installation. Answer these for every TTY on the property before sizing the order.

| Question | Why it matters |
|---|---|
| **Is the TTY on its own analog line?** | A standalone TTY on a published number is the case this post covers. A TTY function built into a 911 call-handling system or a phone system extension is migrated with that system, not line by line. |
| **What is the published TTY number, and where is it published?** | Websites, directories, signage, relay-service records, and the ADA notice all carry it. The number must move with the line, so plan the port with the carrier before cutover. |
| **Who does the line reach today?** | Incoming TTY calls from the public, outgoing calls to relay, direct calls to 911, or all three. Each becomes a row in the test plan. |
| **What TTY model is it, and what modes does it use?** | Most US TTYs use the Baudot mode covered by TIA/EIA-825; some also support ASCII or V.18 modes, and some add turbo or auto-answer features. Note what is in use so the test covers it. |
| **How is the TTY powered?** | A wall adapter, an internal battery, or both, and for how long. This decides whether the 90X1's UPS output or a separate supply is part of the plan. |
| **What is the cellular signal where the line terminates?** | Measure signal at the closet where the 90X1 will sit. A basement telecom room or an interior counter may need an external antenna. |

A hospital will usually find a TTY at admissions, in the emergency department, and in a patient-equipment pool, with one published number. A city will find them at the clerk's counter, the police non-emergency desk, and the 911 center's administrative line. A university will find one at disability services and one at campus safety. The inventory tells you which lines exist; the test tells you whether the replacement works.

## Installation and testing, machine by machine

The installation itself is short. The white paper reduces it to three steps, and the third is the one that matters.

1. **Connect.** Plug the TTY's phone cord into any of the 90X1's eight RJ-11 FXS ports. Label the port with the TTY and the published number it serves.
2. **Configure.** In Ara, confirm that the line uses the G.711 codec for TTY traffic.
3. **Test.** Call another TTY or a relay service (711) and confirm that text types cleanly in both directions.

Complete an end-to-end test from each TTY after installation and record the result per machine. The acceptance checklist below is a starting point; the institution's ADA coordinator, its 911 center, or its insurer may add to it.

| Acceptance check | Pass condition |
|---|---|
| TTY to TTY, outgoing | A full test string typed from the migrated TTY, including every letter, every digit, and the GA and SK sequences, arrives on a second TTY with no dropped, doubled, or substituted characters |
| TTY to TTY, incoming | A call to the published TTY number rings the migrated TTY and the reply string arrives clean |
| 711 relay | A relay communications assistant reads the typed text back accurately and the assistant's typed replies display cleanly |
| Voice carry over or hearing carry over | Where the site uses them, speech and text alternate on one call without the text leg degrading |
| Echo | No doubled characters or stray characters appear on the sending TTY's own screen |
| 911 | A scheduled TTY test call, coordinated with the PSAP in advance, reaches the 911 center with the expected location information |
| Battery | Remove AC power from the 90X1 and repeat a TTY-to-TTY call on battery |
| Supervision | Disconnect the TTY's line and confirm Ara raises the alert |
| Procedure | Staff answer the test call exactly as the written accessibility procedure says, with no new steps |

Coordinate any 911 test call with the local PSAP, and tell your relay provider and your 911 center which TTY numbers are moving and when, so a changed line during cutover is understood rather than treated as a fault. The final installation must meet the site's applicable accessibility (including ADA) and emergency communication requirements, which is why the test, not the connection, is the finish line. Keep the old copper in service until each TTY has passed.

## Planning across a portfolio

A single counter is an afternoon's work. A hospital system, a state agency, or a transit authority runs this as a program:

1. **Inventory every TTY** using the six questions above, including machines kept in a drawer for patient or guest use and the administrative TTY at the 911 center.
2. **Group by closet.** Each closet or equipment room with TTY lines becomes a 90X1 site; a room with more than eight lines, or with other analog lines to migrate, gets a second appliance.
3. **Pilot one site** with the TTY models in use, migrate it, and run the full acceptance checklist, including a scheduled 911 test.
4. **Sequence by exposure.** Published numbers that the public calls go first, then internal and backup lines.
5. **Document the result.** A per-machine record of the test, the Ara configuration, and the closet location is what the ADA coordinator will hand to an auditor, a complainant's attorney, or the next facilities team.

The same inventory serves the other analog lines on the property. Elevator phones, fire panels, and fax machines in a hospital or a city hall share the closets these TTY lines use, so a portfolio migration usually moves them together. Our [nurse call and panic button use case](https://dataremote.com/blog/nurse-call-panic-buttons-pots-replacement) follows the same station-by-station pattern for a facility's call systems, and our [campus blue light phone use case](https://dataremote.com/blog/campus-blue-light-emergency-phones-pots-replacement) covers the dispatch-side testing that a 911 center or campus safety office will recognize.

**Plan your TTY migration:**
Start with the TTY inventory: is it on its own line, what is the published number, who does it reach, what model and modes, how is it powered, and where does the line terminate. Share it with DataRemote and we will help you size the 90X1 deployment and build the machine-by-machine test plan. [Talk to a DataRemote engineer](https://dataremote.com/contact).

## How DataRemote helps

DataRemote builds [POTS line replacement](https://dataremote.com/solutions/pots-line-replacement) around the equipment an institution already has: the TTY keeps its analog line, and only the carrier underneath changes. For text telephones, that means:

- **The 90X1**, a 5G POTS IN A BOX® appliance with eight TTY/TRS-capable RJ-11 FXS ports with surge protection, G.711 audio with G.168 echo cancellation, E911 support with geo-location, an integrated 18-cell lithium battery rated for up to 48 hours of standby, a 12 VDC UPS output for approved devices, and a wired WAN port for failover.
- **Ara**, for confirming the G.711 codec per line, line-status monitoring with alerts, and remote management across every appliance in the portfolio.
- **Tone-carrying experience** from the same platform that carries [fire and burglar alarm communication](https://dataremote.com/solutions/fire-burglar-alarm-communication), where in-band tones have to arrive intact in the same way.
- **The one-page white paper**, [90X1 TTY Machines (PDF)](https://dataremote.com/documentation/marketing/dataremote-90x1-tty-machines.pdf), for the ADA coordinator, the telecom manager, or the 911 director who needs the summary.

Every site is different. TTY model and modes, the published number, who the line reaches, TTY power, and cellular coverage at the closet all affect the design, so each site should be tested on its own before cutover.

## Frequently asked questions

**Do we have to replace our TTY machines when the copper line is retired?**

No. The DataRemote 90X1 presents a standard analog line on each of its eight FXS ports, so the TTY's existing phone cord plugs into the appliance and the TTY, its published number, and the procedures around it stay as they are. Only the line underneath changes, from copper to a TTY/TRS-capable port that carries the TTY's tones as G.711 audio over 5G/LTE.

**Why do TTY calls fail on ordinary VoIP or cellular lines?**

A TTY sends each typed character as a short burst of two audio tones, with no error correction and no retry. A compressed voice codec, a dropped packet, or an echo canceller that clips the start of a tone turns a character into a different one or loses it, and the person reading the screen sees gibberish or gaps. Carrying the call as uncompressed G.711 audio with G.168 echo cancellation, which is what the 90X1 does, is what keeps the characters intact.

**Can a TTY on the 90X1 reach 911 and 711 relay services?**

The 90X1 provides E911 support with geo-location and supports calls through Telecommunications Relay Services, including 711. The FCC advises that in an emergency a TTY user should call 911 directly rather than placing a relay call through 711. Coordinate any 911 test call with the local public safety answering point before placing it.

**Doesn't real-time text replace TTY now?**

For wireless phones, in part. In December 2016 the FCC adopted rules that let wireless providers and handset makers support real-time text (RTT) in lieu of TTY technology, with RTT required to be backward compatible with TTYs. That transition is about handsets and wireless networks. The TTY on a hospital desk, in a government office, or at a 911 center is a wired analog device, and it still needs an analog line that carries its tones, which is what the 90X1 provides.

**Which rules require a TTY line to keep working?**

Under the ADA regulations, 911 and other telephone emergency services must provide direct access to TDD users (28 CFR 35.162); state and local governments that communicate by telephone must use TTYs or equally effective systems (28 CFR 35.161); and businesses that offer customers or patients outgoing calls on more than an incidental basis must make TTYs or other accessible telecommunications available (28 CFR 36.303(d)). FCC rules require PBX operators and interconnected VoIP providers to support 711 dialing. None of these says how the call must travel; each says it must get through.

**What happens to the TTY line during a power outage?**

The 90X1 keeps the line live from an integrated 18-cell, 15 Ah lithium-ion battery rated for up to 48 hours of standby (actual runtime varies with usage), and its 12 VDC UPS output can power an approved connected device. The TTY itself needs its own power; many run from a wall adapter with an internal battery, so check both before cutover. The FCC notes that traditional copper landlines typically work during power outages while modern alternatives usually need backup power.

---

Canonical page: https://dataremote.com/blog/tty-machines-pots-replacement
Organization: DataRemote, Inc. — POTS line replacement, cellular failover, and fixed wireless access solutions. https://dataremote.com