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Why can't my PC communicate with my colleague's TTY?

For general advice, you may want to contact the expert: Norman Williams <>. He can also be reached on the telephone at (202) 651-5257.

Concerning communicating between PC's and TTY's:
There is a lot of good up-to-date info on this at which is the WWW site for the Technology Assessment Program at Gallaudet's Research Institute.

(Contributed by William Flis at 14 Jun 1995.)

Thomas McLaughlin from NXi Communications, Inc. wrote articles, which describe the various practical difficulties in establishing communication with standard modems. You may find his articles in the NXi Corp. Web site.

I have an IBM-compatible personal computer. Can I call a TDD user?

Yes, but only if you have a Weitbrecht/Baudot-compatible modem. First a quick explanation about why computers can't communicate with TDDs. The two systems are basically incompatible because each uses a different coding system to transmit messages over telephone lines.

Computers use ASCII code, while most TDDs use Baudot which has a fixed baud rate of 45.45. (However, some of the newer TDDS allow users to select either Baudot or ASCII up to 300 baud.)

If you want to call a deaf person who has a TDD that can use up to 300 baud ASCII, you can use a REGULAR Hayes-compatible modem (preferably 300 baud). You will not need to buy a special modem because the deaf person's TDD can be switched to ASCII either manually or automatically (upon receipt of your incoming ASCII call).

To call a deaf person who has a Baudot TDD, you will need to buy a special kind of modem. There are a few available; your choice depends on whether you already have a regular Hayes-compatible modem or have never had a modem.

TTY-compatible external modems

Unless a date was explicitly stated, the following information is up to date as of November 1993. Please inform the author of any inaccuracies.
  • Computer Modem (CM-4), sold by Phone-TTY.

    Contact information:
    Phone-TTY, Inc.
    202 Lexington Avenue
    Hackensack, New Jersey 07601
    (201) 489-7890 TDD
    (201) 489-7889 Voice
    (201) 489-7891 FAX

    They sell their Phone-TTY CM-4 modem and the IBM PC software Futura-TTY as a package for $359.

    (Contributed by Troy Goodson at 9 Jan 1995.)

  • UNI-PTC, sold by Integrated Microcomputer Systems, Inc.

    Contact information:
    Integrated Microcomputer Systems, Inc.
    2 Research Place
    Rockville, Maryland 20850
    (301) 869-6391 (TDD/ASCII)
    (301) 948-4790 (voice)

  • IBM PhoneCommunicator, by IBM.

    Contact information:
    IBM Special Needs Informaton and Referral Center
    2500 Windy Ridge Parkway
    Marietta, Georgia 30067

    1-800-IBM-2133 (Continental USA, voice)
    1-800-284-9482 (Continental TDD)

    Note: the voice number was reported at 21 Nov 95 to be wrong. If you have more up-to-date information and/or correct number, please E-mail it to Omer Zak.

  • A Baudot/ASCII modem (no model name given) developed by AT&T/NCR, Rockville, MD.

    Contact information:
    (301) 212-5481 TTY
    (301) 212-5479 Voice

  • InteleModem

    This is a device which allows your computer to talk to a TDD. The device is an external modem that connects to the RS232 connector of your MAC. It will automatically switch between TDD at the proper baud speed and the Baudot code to ASCII at the computer speed (300 on up). If you would like more information, send a note to

    (Contributed by at 21 Jul 1994.)

  • See also the NXi Corp. Web site.

TTY- and IBM PC-compatible hardware

  • The NXi Corp. TTY modems product line
  • The HITEC Group Int'l, Inc. two different brands of TDD compatible modems: the Ultratech Intellemodem, and Nexion's Nexcom 300.

    Contact information:
    HITEC Group Int'l, Inc.
    8160 Madison
    Burr Ridge, IL 60521

    800-288-8303 (Voice/TTY)
    708-654-9200 (Voice/TTY)
    708-654-9219 FAX

    E-mail: <> or <>.
    WWW site:

    (Contributed by at 18 Jul 1995 and updated at 4 Dec 1995.)

  • A neat TTY/keyboard combo is available from HITEC Group Special Needs Center. It is called the KeyPlus.

    HITEC's 800 number is (800)288-8303.

    (Contributed by Chelestr at 20 Sep 1995.)

  • Another company, which manufactures plug-in TTY cards: The DEAFWORKS Company.

TTY- and IBM PC-compatible software

Unless a date was explicitly stated, the following information is up to date as of November 1993. Please inform the author of any inaccuracies.

    This program was developed by Norman Williams <> at Technology Assessment Program of Gallaudet.

    It is available from:

    1. Handicap News ftp site, "" in the /pub/hearing directory. In that same directory, there are also other TDD related programs, sign language tutor programs, ASL fonts, etc. The directory has a file called 00-index.txt which is the index file.
    2. Futura Wave Communications's BBS at (202) 544-3613. Also Futura 3.0 files are available from this BBS (see below). Since 29 Jan 1996, they have their own WWW site at:
    3. Anonymous FTP from Download /tap/

      (Contributed by William Flis at 16 Jun 1995.)

  • TDD56

    [I have no information about this package.]

  • Futura 3.50

    This program was developed by Norman Williams <> at Technology Assessment Program of Gallaudet.

    It is available from:

    1. Phone-TTY
      (201) 489-7889 Voice
      (201) 489-7890 TTY/ASCII
      (201) 389-7891 Fax
      (Major credit cards accepted)
    2. The demo version of Futura-TTY 3.0 is available via anonymous ftp from "" as "" in the /pub/hearing directory. Also available via dial-up from the Handicap News BBS 1-203-926-6168.
    3. Futura Wave Communications's BBS at (202) 544-3613 and their WWW site at
  • NOTEKS - Texttelephone-program

    This program is not really an emulation program, but a TDD program which works according to the TDD standard in use in Norway. This program is readily customizable to work with any language whose direction of writing is from left to the right.

    To obtain a copy of this program, contact:

    Jan Berntzen
    Telenor Research and Development
    P.O.Box 83
    N-2007 Kjeller, Norway
    Office: Instituttveien 23

    Voice: +47 63 84 86 61
    FAX: +47 63 81 00 76

    E-mail: Internet <>

    Last updated: 30 Oct 1995.

  • WINdial

    WINdial is a new text telephone program for Windows, which is presently under development. For more information, contact Jan Berntzen <>

    Last updated: 30 Oct 1995.

TTY- and Macintosh-compatible hardware

Dove Corp. (from Wimnington, NC, USA) used to make a Macintosh TDD modem with a modified version of Microphone. However, they went bankrupt.

(Contributed by Joe Clark at 2 Jan 1994 and updated at 12 Oct 1995.)

TTY- and Macintosh-compatible software

  1. There is a program called Soft-PC running EGA/AT or higher that can run Futura-TTY on MAC using the Ultra-Tec Intele-modem.

    (Only TTY/ASC modem that can communicate with Futura-TTY on MAC only) For more information, please call Phone-TTY, Inc.

    201-489-7889 Voice
    201-489-7890 TTY/ASCII
    201-489-7891 FAX

    (Contributed by Phil Jacob <> at 3 Jan 1994.)

  2. Smartcom II (part #08-00107)
    Manufactured by:
    Hayes Microcomputer Products, Inc.
    P.O. Box 105203
    Atlanta, GA 30348

    Should be available in any computer store.

    (Contributed by Jenifer Dean at 10 Jul 1995.)

TDD standards in various countries.

Approval of V.18

The following was contributed by Stephen Satchell (Compuserve: 70007,3351) via Bill McGarry at 11 Jul 1994.

I got word from Geneva that the following V-series Recommendations have been approved and are now real:

  • V.8 -- Calling-tone menu (part of V.34 startup sequence)
  • V.18 -- TDD modulation methods (finally)
  • V.34 -- Adaptive rate to 28.8 kilobits/s over switched network
  • V.58 -- Network management modem information blocks (MIBs)

The V.18 passage paves the way for inexpensive modems to incorporate support for TDD terminals. This means that modems offering this capability could be used by anyone with a computer terminal to accept indial from a TDD. Conversely, a deaf person can use a standard modem (which implements V.18) in place of a dedicated device.

V.34, aka V.Fast, defines a modem modulation scheme which permits two compliant devices to communicate at a negotiated speed ranging from 4.8 kilobits/s to 28.8 kilobits/s in increments of 2.4 kilobits/s. Further, proper use of the probing tones by the compliant modems permits those modems to select the optimal symbol rate and signal constellation at the beginning of the call. In other modulation methods, the modems had to experiment with the connection in progress to find the optimal equali- zation and speed for a given connection.

V.58 defines a standard way of describing modem capabilities. Originally intended for local area network and wide-area network management, there are people looking to incorporate this system in "desktop managers" as well.

In further news, the AT command set definition is now an offical project (in ITU parlence, there is a Question in the current Study Period) with the goal of defining a new Recommendation V.25 ter. One source has gone out on a limb and said that a ballot could be out as soon as next summer.
My prediction is 18 months.

(c) Copyright Satchell Evaluations 1994 -- The above may be redistribu- ted, but not for profit.

ITU Recommendation V.18 was approved in September 1994. Contact Dick Brandt, for more details.

History of V.18 modems operating in the text telephone mode

History of V.18 Standard

[1] The V.18 standard (V.txp), is the operational and internetworking requirements for modems operating in the text telephone mode.


[2] When Telephone Administrations were phasing out their low speed printer services some of them made these obsolete electrical terminals available to the deaf community. The technology embedded in these terminals, half duplex, low speed/Baudot (IA2) coding, has been carried through to today in modern TDDs. This adherence to this old technology has greatly limited the deaf community's access to today's on-line information services. In 1991 there was work underway to create a new modern TDD which will incorporate (ASCII (IA5) and a modern modem. One of the major obstacles to movement to this new technology was the need to main6tain compatibility with the large installed base of the older IA2 machines. Any scheme developed for interworking between these new terminals needs to be as automatic as possible as many of the deaf community are older people who would find it difficult to handle complicated set up procedures.

Given the above a study was conducted of an Appendix to Recommendation V.22 bis that would allow for automatic interworking between existing Telecommunications Devices for the Deaf (TDD) terminals and other DTEs using modems conforming to CCITT Recommendations V.22 bis.

The goals were:

  1. allow those with existing TDDs to interconnect and communicate with a larger range of people and services.
  2. allow for gradual phasing in of new TDDs equipped with V.22 bis modems.

Considerations of the Study:

  1. Older TDDs (prior to V.22) use 1800 Hz/1400 Hz FSK half-duplex operation with an approximate baud rate of 45.5 in the U.S.A. and 50 in Europe.
  2. IA2/IA5 conversion should take place in the modem. (5 bit Baudot to 7 bit ASCII)
  3. Signal, generated by the calling party, is needed as the phone may be answered by a "hearing" person who needs to be aware this is a TDD call. (V.25 calling tone?)
  4. The protocol developed is able to accommodate extended quiet periods at the beginning of the sessions as in many cases the deaf person using an older TDD may not be aware the called party has answered or there may be a delay going from the voice mode to the TDD mode (many existing TDDs are acoustically coupled).

Recommendation for doing the study:

Community leaders through the world have recognized that the deaf community needs to be allowed to participate in the "Information Age" through improved access to the growing number of on-line information services available as well as the ability to communicate with hearing friends through home PCs. This should not require them to incur the expense of having two terminals/modems: one for communicating with TDDs and one for other services. This latter concern also applies to many hearing people who would like to be able to communicate with their hearing impaired friends without the complication and expense of acquiring an switching between two separate modems.
CCITT is in the unique position to help the deaf community by providing an international solution to this problem. It was therefore recommended that CCITT undertake the study of developing a "Procedure for automatic interworking (Automoding) between Recommendation V.22 bis modems and TDDs. The use of Recommendation V.22 bis modems was proposed as they were becoming the "standard" modem for most on-line applications, as well as PC-based communications at the time.

As a result of the study, The XVII Study Group then produced what is called the V.18 standard. The Final Draft of the Recommendation V.18 was submitted for approval Geneva 1-9 June 1994.

At the Meeting , all 15 Members present proposed that the approval procedure be initiated.

I would like to thank Texas Instruments Incorporated and Augment Systems Incorporated for the information.

1. Proposed approval of four new Recommendations agreed to by Study Group 14 at its meeting on 9 June 1994, International Telecommunications Union, Telecommunication Standardization Bureau, Geneva, 20 June 1994, ref TSB Circular 82 COM 14/YS, signed by Th. Irmer, Director of the Telecommunications Standardization Bureau

2. Telecommunications Device Devices for the Deaf (TDD)/V.22 bis, CCITT Interworking Study Group XVII Delayed Contribution D93 Geneva 29 April-3 May 1991

3. Final Draft of Recommendation V.18, Study Group 14/WPS Rapporteur on Question 8/14 (Mr. R.P. Brandt, U.S.A. Geneva, 1-9 June 1994

(Contributed by Stephen Pomfret, Augment Systems, 19 Crosby Drive, Bedford MA 01730-1419, TDD (617)275-4510 at 28 Oct 1994.)


New standard: Bell 103, ASCII, 300 BPS, 8N1
Old standard: Weitbrecht, Baudot, 45.5 BPS

A reference for the old standard:
JUNE, 1986
Prepared by the EIA Engineering Committee TR-41
Ad Hoc Committee on Telecommunication Devices for the Deaf

Great Britain

Contributed by Andrew J. Cowie at 1997 January 01.
Preferred standard : - CCITT V.21 300bps 8N1
Also in use        : - Baudot 45.45bps


Most TTYs in use in the UK are imported Ultratec products, which offer ITU-T V.21 @ 300 bps (NB! NOT Bell 103!), and Baudot 45.45bps, and most models have some autoswitching between Baudot and CCITT. The level of sophistication of the autoswitching is higher in the newer models.

Some older textphones in use in the UK are V.21 Only, or V.23 mode 2 (1200/75 bps) only. New purchase of such machines is discouraged, and the latter can now only be used to contact the National Relay Service ("Typetalk").

The main UK relay is currently ITU-T V.21, V.22, and V.23 compatible only, no Baudot support, although this is planned. The UK relay service also provides access to the Emergency Services through a dedicated, high priority number. This number supports the same ITU-T standards as the main relay PLUS Baudot.

UK Relay contact Information:

     RNID Typetalk
     John Wood House
     Glacier Building
     Harrington Road
     Brunswick Business Park
     L3 4DF
     Great Britain

     +44 151 709 9494 Voice
     +44 151 709 8119 Fax
     0800 592 600 Technical Support (Textphones only)
     0800 500 888 Registrations (Textphones only)
     0800 592 593 Billing/Rebates (Textphones only)

     0800 51 51 52 Relay calls (voice callers)
     (+44 151 494 2022 from outside UK)
     0800 95 95 98 Relay calls (CCITT textphones only)
     (+44 151 494 1260 from outside UK)
     0800 112 999  EMERGENCY SERVICES (CCITT/Baudot textphones only)

     NB - 0800 numbers can only be dialled from within the UK.


Contributed by Omer Zak:

FAX machines are being used. For modem conversations, use the following: Bell 103, ASCII, 300 BPS, 8N1. The Hebrew letters are encoded according to Israeli Standard 960.

A copy of the proposed Israeli TDD standard is available in the Deaf Gopher. To access a short summary, click here.

New Zealand

Contributed by Barry Kirkland:

Baudot, I'd say, but it's a bit of a monkey's jungle like it is in America and England. I don't know if ASCII is in wide use in NZ.

[Other countries - please give information.]

TDD abbreviations

The following are commonly used abbreviations used by "TDD'ers":
As soon as possible
Good bye
CD or CLD or CUD
See you later
What to do?
Go Ahead
About to hang up
Love you
Oh I see
Q or QQ
Let's wait and see
Send Kill (or Stop Keying) - End the call
Hanging up
Erases an error
Showing emotion
Use exclamation points just as you use them if you were writing a letter. The operator should understand this, and s/he should also understand that you're fired up about something (or depressed about something, etc) by the speed you type. Being a hearing person that's been on the other line, some operators express this rather well.

(Contributed by Heather M. Riddle, interpreter for the Deaf, at 25 Jun 1995, by John Campbell at 29 Sep 1995 and by Vikee Waltrip <> at 30 Sep 1995.)

Two-line VCO

Many of you have heard of the Voice Carry Over (VCO) feature of Telecommunication Relay Systems (TRS).

Stephanie Buell of Wisconsin TRS spoke about a novel extension of VCO at the recent SHHH convention in Baltimore called `Two Line VCO'. Two-Line VCO enables users to talk and be talked to simultaneously, and can be used with ASCII TTYs or PCs.

With conventional VCO, conversations are more structured and may be slower since ASCII cannot be used with "standard" VCO. Thus conversations with two-line VCO are more interactive, spontaneous and "real-time". It is the closest thing yet to true "functional equivalence" of telephone usage.


  1. Two separate phone lines
  2. A telephone plan purchased from your Local Exchange Carrier with three-way calling (also known as conference)
  3. A direct connect ASCII TTY or PC equipped with a modem


  1. Call TRS on DATA line using ASCII TTY or PC
  2. Type to Communications Assistant (CA) that this will be a two line VCO call
  3. Instruct CA to call you on other phone (VOICE)
  4. Answer the voice line with your voice (to allow the CA to distinguish your voice from other voices) and tell CA you will be conferencing another person into the call, and NOT to type your speech at all!!!!
  5. On voice line, say `Please hold' to the CA
  6. Press FLASH or HOLD on phone
  7. Dial the number of the person you want to call on VOICE line
  8. Press CONFERENCE or whatever is the button for three way calling.

When the called party answers, the CA will immediately start typing. So as soon as you see `Hello' or whatever is on the DATA line, you can start talking. Moreover the other person has no idea that you are using TRS. The CA will type only the other person's speech which is read on the DATA line.


The CA will NOT communicate with the third party but the CA will indicate if the third party is talking too fast or whatever thus you would have to ask the third party to slow down i.e. you are in control of the whole process.

The caller also has the flexibility of hanging up on the called party without losing connection with the CA. An additional advantage is that it will be easier to deal with pre-programmed dialing for calling cards, 900 numbers, automated recorded menus etc.

Most offices have the facilities that allow two-line VCO to work so make use of these before you decide to make the investment of a second phone at home.

For those of you with hearing aids or cochlear implants, this can also provide excellent auditory training.

Contact information

Stephanie Buell of the Wisconsin TRS can be contacted at:
TTY 608 833-3898
FAX 608 833-3208

(Contributed by Tilak Ratnanather at 22 Aug 1994.)

TDI contact information

To subscribe to TDI nationwide TTY directory and GASK newsletters for only US$15 and get updated information on modems etc, contact:

Telecommunications for the Deaf Inc.
8719 Colesville Rd., Suite 300
Silver Spring, MD 20910

Be sure to include your TTY number so that it will be listed in the next edition of the TTY directory.

(Contributed by Al Sonnenstrahl at 16 Dec 1993.)

Internet provider's TTY/TDD service

An Internet provider with deaf customers would not need to provide special TTY/TDD access service if it uses its existing facilities as follows.

Customers are likely to have two classes of problems which might require support from the Internet provider:

  • Customer can log into his account and do things there.
  • Customer cannot log into his account.

If the customer cannot connect to the Internet provider's modem at all, he has a problem with his system or with the phone line. In this case, the customer should contact his computer system vendor's service personnel or the phone company.

If the customer can log into his account, then the standard Unix 'talk' program will do the job of communication with the Internet provider's customer service personnel even better than most TDDs (which are limited to one 20-character line).

To handle the case, in which the customer can connect to the Internet provider's computer but not log into his account, the Internet provider may define a special account as described below. In the following description, this special account is assumed to have the username 'talk'.

The 'talk' account would have no password, and would allow the customer ONLY to invoke the 'talk' program to talk with the Internet provider's customer service personnel. Using this special account, the customer and the customer service personnel will talk about the customer's problems with his account.

Where can I find Robert Weitbrecht's biography?

This is a question which Omer Zak asks once in a while, often accompanied with some explosive words.

Regretfully, there is no complete biography yet. However, according to Tilak Ratnanather, as of 16 Mar 1995, three or four people are competing with each other to write up a book on the history of telecommunications devices for the deaf. So sooner or later, there will be an extensive biography of Robert Weitbrecht.

Until such a moment, one should be satisfied with a chapter which mentions the work of Robert Weitbrecht in Harry Lang's "Silence of the Spheres: The Deaf Experience in the History of Science" published by Bergin & Garvey (187 pp, $49.95 list price; $39.96 with a 20% discount if you call the publisher at 800 225 5800; the discount expires March 31,1995)

Last update date: 
1997 May 3