Public TTYs: Description and Methodologies for Free Calling
From DocDroppers
| Author: | dual_parallel |
|---|---|
| Date Released: | Unknown |
| Added to DD: | 02:18, 19 Dec 2004 (EST) |
Contents |
Introduction
With the advent of wide-spread electronic connectivity, one might think that the deaf, hard-of-hearing and speech impaired (hereon called deaf) have unfettered access to limitless communication. Email, text and instant messaging are convenient, but access is not always possible regardless of disability. This is where public TTYs fill an important gap in accessibility.
TTY stands for TeleTYpewriter, or sometimes Text TYpewriter. Teletypwriters are devices that enable the sending of text messages using modulation and have been used by hams for decades. TTYs formed the basis of the technology that is now the modern Telecommunication Device for the Deaf, or TDD. By convention, deaf TDD users call the devices TTYs.
The creation of the TTY began in 1964 when a deaf physicist named Robert H. Weitbrecht, with the help of others, decided that deaf people should be able to use the telecommunications system as easily as a hearing person. (The full story of the TTY's creation is told in Harry G. Lang's book, A Phone of Our Own.) This creation of a few men almost 40 years ago is still an important part of accessible telecommunications.
This article will address publicly available TTYs; legislation regarding their placement, the basis of their technology, and methods for making relay calls at no cost.
Legislation
Enacted July 26, 1990, the Americans with Disabilities Act (ADA) protects the civil rights of the disabled. The four main titles of the ADA (Title I - Employment, Title II - Municipal Services, Title III - Public and Commercial Locations, and Title IV - Telecommunications) mention the use of TTYs. The requirements of Titles II and III, which concern most public locations, can be summarized by the following:
- Newly built venues with four or more public pay phones, one being an interior phone, must have a TTY on site
- Existing facilities that are adding pay telephones to bring the total on site to four with one interior phone must have a TTY
Other regulations can be met with the inclusion of a shelf and power outlet at pay phones or courtesy TTYs.
Title IV, Telecommunications, creates the Telecommuncations Relay Service (TRS) that exists in every state and is available 24 hours a day. Funding for TRS is normally collected as a surcharge listed as a "Telecommunications Relay Service Surcharge" on Local Exchange Carrier (LEC) phone bills. These charges pay for toll-free relay numbers and relay operators, or Communications Assistants (CA) as they are officially called.
Technology
Public TTYs usually consist of Fortress or Millenium pay phones with an enclosed, motorized drawer mounted underneath the phone housing. When the TTY encounters TTY tones from a dialed number, the drawer will open to reveal a ruggedized keyboard and a one-line LED display. A red LED adorns the front of the drawer, which responds to data transfer, ringing and voice during coventional calls. Courtesy TTYs are usually accoustically coupled TDDs.
The basis of TTY technology is the Weitbrecht modem. The Weitbrecht modem uses Frequency Shift Keying (FSK) modulation and the Baudot code character set to transmit data at a rate of 45.5 baud (bps). Frequency Shift Keying is the use of two analog waves at different frequencies to represent ones and zeros. The Weitbrecht modem uses 1400 Hz for the mark (1) and 1800 Hz for the space (0). So as the TTY user types a message, the TTY converts the entered characters, using the Baudot code set (see Table 1), into the buzz-like beeping that can readily be heard.
Other standards for TTY communication exist, like Bell 103 and Turbo Code. Bell 103 transmits at 300 bps and uses the ASCII character set. Turbo Code transmits at 110 bps and, more importantly, transmits data as fast as the user can type and allows for conversation interruption like voice calls. Turbo Code is implemented in all Ultratec, Inc. TTYs, the most commonly encountered public TTY.
Table 1: Baudot Code
BINARY HEX LTRS FIGS ====== === ==== ==== 00011 03 A - 11001 19 B ? 01110 0E C : 01001 09 D $ 00001 01 E 3 01101 0D F ! 11010 1A G & 10100 14 H # 00110 06 I 8 01011 0B J BELL 01111 0F K ( 10010 12 L ) 11100 1C M . 01100 0C N , 11000 18 O 9 10110 16 P 0 10111 17 Q 1 01010 0A R 4 00101 05 S ' 10000 10 T 5 00111 07 U 7 11110 1E V ; 10011 13 W 2 11101 1D X / 10101 15 Y 6 10001 11 Z " 01000 08 CR CR 00010 02 LF LF 00100 04 SP SP 11111 1F LTRS LTRS 11011 1B FIGS FIGS 00000 00 ===UNUSED===
Methodologies
The following methodologies will teach the reader how to make free toll or local calls from a public TTY. No matter what the circumstance, relinquish the use of any public TTY to any deaf person who wishes to use it.
The first method for making free calls with a TTY is to simply ask. Courtesy TTYs are widely available and people are generally more than happy to let a hearing person use one. The TTY will more than likely be an accoustically coupled TDD and the probability of making toll calls is low.
The second method concerns pay phone TTYs and is slightly more involved. There are a few prerequisites to make these calls: a toll-free TTY relay number, a way to op divert, an ANAC number and the number you are calling. General knowledge of IntereXchange Carrier (IXC) switching may be helpful.
Now, TTY pay phones can be found at malls, airports, universities and other areas meeting ADA requirements (see Appendix A). TTY relay numbers for the 50 states and more can be found at:
http://data.club.cc.cmu.edu/~red_trek/relay.html
There are many ways to op divert to toll-free numbers and many texts written about it. Published ANAC numbers are also plentiful - a little research will go a long way. Regarding the number you are calling, you may not want to call a number associated with you. With info in hand, here is the method for making the call:
- Op divert to an ANAC. If the ANAC does not read back the number of the pay phone, you have ANI fail and you can continue.
- Op divert to a toll-free relay number.
- The CA will ask for the number you are calling from. Enter a random, but realistic number.
- You will then be asked for the number you are dialing and the call will be completed.
Note the number read back from the ANAC. There is a good chance it will read back the NPA of the IXC regional center. To increase your chances of call completion, call a relay op and number within that NPA.
The third method deals with telcos that use 711 relay service. Dialing 711 from a pay phone, or a subscriber line for a courtesy TTY, will automatically dial a relay op. From here, three things could happen. At a courtesty TTY you will be able to make local calls like method one. Next, at a pay phone, the relay op could ask for the method of payment and no call will be made. Last, and best, is that no ANI will be passed and the call will be completed similar to the second method.
The final calling method involves TTY relay, but it utilizes public computers instead of telephones. Publicly available computers are abundant; libraries, broadband company kiosks, demonstration computers, etc. And making a nationwide relay call is as simple as using a Java-enabled browser. AT&T Relay Service, found at http://www.relay.att.com/national/relay.html is a free, browser-based relay service provided by AT&T. Currently, only Windows operating systems are officially supported, with browser support limited to Netscape 4.7 and later and Internet Explorer 5.0 and later. Conversations are encrypted and can be printed for later perusal. Using the service is straight-forward: enter the number to be dialed, click Connect and you will be greeted by an AT&T CA.
Some pitfalls you may encounter include called party confusion from talking to a relay op and subsequent disconnection. Another obvious drawback is the realy op not believing you and not connecting the call. Other than that, these methodologies are effective.
Conclusion
Where hackers may seem preoccupied with breaking security, it may be easy to say that phreaks are only concerned with making free telephone calls. This is not the case. Computer security is just another fulfilling challenge that knowledge-hungry hackers cannot resist. Cost-free calling is a product of exploration - finding new and different ways to use telecommunications technology.
The technology of TTYs may seem basic, but their history, importance and current technological development make omission of TTYs in a phreak's repertoire folly. There are many advancements left to explore, like TTY printers, Voice Carry Over (VCO) and telephone captioning. Enjoy the technology of TTYs with the true spirit of a hacker.
Appendix A - Concerning Public TTY Locations
Unfortunately my LEC, Qwest, does not maintain a database of TTY pay phone locations. Not to preach, but the Qwest Center for Customers with Disabilities (PO Box 1355/400 Tijeras Ave. NW; Albuquerque, NM 87102-1355; Voice/TTY 800-223-3131; FAX 505-765-8203) should be ashamed that something as simple as a list of TTY pay phones does not exist. I will concede that one Qwest employee said he would pass on the idea of a TTY database to his superiors. Until that time, I have taken it upon myself to compile a list of pay phone and courtesy TTYs in my local calling area. I _will_ be sending this list to Qwest.
- Albuquerque Convention Center - Qwest Fortress / Ultratec PP2M120 - 505-242-0710
- Albuquerque International Sunport - Qwest Millenium / Ultratec PPT1 - 505-245-9092
- Albuquerque International Sunport - Bag Claim 5 - Qwest Millenium / Ultratec PP2M120 - 505-245-9141
- Albuquerque International Sunport - Gate A3 - Qwest Millenium / Ultratec PPT1 - 505-245-9111
- Albuquerque International Sunport - Gate B4 - Qwest Millenium / Ultratec PPT1 - 505-245-9094
- Century Theaters Downtown Albuquerque - 214 2nd St. SW - COCOT / Ultratec TTY - 505-924-9645
- Coronado Center - Louisiana & Menaul - 2500 telephone set / Ultratec Minicom IV - 505-872-8161
- Cottonwood Mall - 10000 Coors Blvd. Bypass NW - Qwest Millenium / Ultratec TTY - 505-898-9804 (Inoperable!)
- TVI Main Campus - Student Services Building - Qwest Millenium / Ultratec PP2M120 - 505-843-9072 (Inoperable!)
- TVI Montoya Campus - Wiley Hall - Qwest Fortress / Ultratec PP2M240 - 505-299-9750
- Winrock Mall - I40 & Louisiana - Qwest Millenium / Ultratec PP2M120 - 505-883-9403
Appendix B - Internet Resources
- A Phone of Our Own by Harry G. Lang
- Access-Able Relay and TTY Phone Numbers
- AT&T Relay Service
- MCI IP Relay
- Qwest Center for Customers with Disabilities
- Sprint Relay Online
- Ultratec, Inc.
Appendix C - TTY Abbreviations
- ABT
- about
- ASAP
- as soon as possible
- ASST
- assistant
- BIZ
- business
- BLDG
- building
- BYE
- good bye
- CD/CLD/CUD
- could
- CUL
- See you later.
- CUZ
- because
- DO-DO
- What to do?
- DOC/DR
- doctor
- EDU
- education
- FIGS
- figures
- GA
- go ahead
- GA SK
- about to hang up
- HD/HLD
- hold
- ILY
- I love you.
- IMPT
- important
- LTRS
- letters
- MSG/MSGE
- message
- MISC
- miscellaneous
- MTG
- meeting
- NBR/NU
- number
- OFC
- office
- OIC
- Oh, I see.
- OPR
- operator
- PPL
- people
- PLS/PLZ
- please
- PRO
- professional
- Q/QQ
- question
- R
- are
- SEE-SEE
- Let's wait and see.
- SERV/SVC
- service
- SD/SHD/SHUD
- should
- SK
- stop keying
- SKSK
- hanging up
- THKS/THX
- thanks
- THRU
- through
- TMR/TMW/TOM
- tomorrow
- U
- you
- UR
- your
- URS
- yours
- WUD
- would
Acknowledgements
Agents of Freedom, DDP, Hackermind, Outbreak and mut3 for the 711 info
