molloy@emerald.uucp (Phil Molloy) (12/08/90)
A friend of mine would like to be able to contact her brother who has
a TTY connected to his phone line. She has access to various modems
and computers to dial her bother's phone, but doesn't know if it is
possible to communicate with this piece of equipment. I don't know
what kind of modulation/demodulation scheme is used by the TTY. Does
anyone out there know if what she wants to do is possible or should
she simply by another TTY and do it that way? The ability to do it
from a modem would broaden here access to him, allowing her to call
from home via a PC or work via her workstation.
E-mail of any help would be greatly appreciated.
(BTW I don't know if TTY is a brand name, reference to Teletype, or
what. It's all she gave me for info).
Thanks,
Philip E. Molloy H71 | Internet: teradyne!molloy@ism780c.isc.com
Teradyne Inc. | difrel!molloy@mit-eddie.edu.com
321 Harrison Ave. | UUCP: {csun, ism780c}!teradyne!molloy
Boston, Ma. 02118 | Phone: (617) 482-2700 x 3678 tnixon@uunet.uu.net (Toby Nixon) (12/14/90)
In article <15335@accuvax.nwu.edu>, molloy@emerald.uucp (Phil Molloy) writes: > A friend of mine would like to be able to contact her brother who has > a TTY connected to his phone line. She has access to various modems > and computers to dial her bother's phone, but doesn't know if it is > possible to communicate with this piece of equipment. I don't know > what kind of modulation/demodulation scheme is used by the TTY. Does > anyone out there know if what she wants to do is possible or should > she simply by another TTY and do it that way? Telecommunications Devices for the Deaf (TDD) are sometimes called "TTY" because the earliest ones were indeed based on Teletype hardware; the newer ones are sleek, compact, battery-powered, with LED or LCD displays and quite portable. TDDs use a special, unique half-duplex modulation scheme at 45.45 baud, which is unlike any that are used in commonly-available modems. The carrier is turned on and off for each character as it is typed, rather than being continuously on all the time, and both TDDs on the line use the same frequencies. Therefore, you can't use a standard modem to communicate with a TDD. Also, TDDs use five-bit Baudot code rather than 7- or 8-bit ASCII code, so most standard comm software won't work, either. There _are_ TDDs in existence which use Bell 103 modulation and ASCII code, but they aren't very common. And, you can also find special modems (from companies such as Krown and Ultratec) that support both Bell 103 and TDD modulation schemes and also automatically translate between ASCII and Baudot, but these cost as much as many 2400bps modems. Telecommunications Industry Association committee TR-30.1 has a project open to define a standard method for automatic interworking between data modems and TDDs. Once this standard is developed, we may see many more modem companies begin to include TDD modulation in standard PC-class modem products. Your friend will need to either buy a TDD (they're not all that expensive; $300-$500), or buy her brother a PC and a modem (which would be a nice Christmas gift, and open up to him the whole world of BBSing). Toby Nixon, Principal Engineer | Voice +1-404-449-8791 Telex 151243420 Hayes Microcomputer Products Inc. | Fax +1-404-447-0178 CIS 70271,404 P.O. Box 105203 | UUCP uunet!hayes!tnixon AT&T !tnixon Atlanta, Georgia 30348 USA | Internet hayes!tnixon@uunet.uu.net [Moderator's Note: For further information, readers are referred to the file on this subject in the Telecom Archives mentioned earlier. PAT]
Tad.Cook@cs.washington.edu (12/18/90)
In article <15419@accuvax.nwu.edu>, hayes!tnixon@uunet.uu.net (Toby Nixon) writes: > Your friend will need to either buy a TDD (they're not all that > expensive; $300-$500), or buy her brother a PC and a modem (which > would be a nice Christmas gift, and open up to him the whole world of > BBSing). I have found that several of my hearing impaired friends have TDDs from Krown and UltraTech which will support 300 bps ASCII. They tell me that many of the newer Terminal Devices for the Deaf have an "ASCII switch." I helped a hearing impaired friend shop for a computer, and I installed a 2400 bps modem and terminal software for her. She found modem communications in the chat mode quite liberating. With a TDD, it is really a simplex operation. At the end of your thought, you type "GA" (for go ahead), and the other party starts typing. Then when they are through, they type GA and you type. In chat mode with the computer, the screen was divided with the sending end displayed on the bottom, and the receiving end on the top. Not only that, but you get a full character set, rather than Baudot code with caps only. We could both type at the same time, and we soon found ourselves having more of a "normal" conversation ... interrupting each other and everything. Tad Cook Seattle, WA Packet: KT7H @ N7HFZ.WA.USA.NA Phone: 206/527-4089 MCI Mail: 3288544 Telex: 6503288544 MCI UW USENET:...uw-beaver!sumax!amc-gw!ssc!tad or, tad@ssc.UUCP
penguin@gnh-igloo.cts.com (Mark Steiger) (12/20/90)
The old Apple-Cat modems can also be used to connect to TTY machines. Also to TDD machines. [ Mark Steiger, Sysop, The Igloo 218/262-3142 300/1200/2400/9600 (HST/Dual)] ProLine.:penguin@gnh-igloo America Online: Goalie5 UUCP....:crash!gnh-igloo!penguin MCI Mail......: MSteiger Internet:penguin@gnh-igloo.cts.com [Moderator's Note: Do you mean they had a switch-selectable setting allowing them to work both ways? I had one and don't remember it. PAT]
peter@ficc.ferranti.com (peter da silva) (12/21/90)
In article <15495@accuvax.nwu.edu> hpubvwa!ssc!Tad.Cook@ cs.washington.edu writes: > I helped a hearing impaired friend shop for a computer, and I > installed a 2400 bps modem and terminal software for her. She found > modem communications in the chat mode quite liberating. My sister in law is deaf, and at various times I have given her a terminal, a modem, and all sorts of information about the same. She now has a PC with a modem ... and after all that, she just called us via one of those deaf-relay operators. She found it too much trouble to arrange a time to call us directly. Sigh. Peter da Silva +1 713 274 5180 peter@ferranti.com