Also sprach Jamie Lokier >Jeff Mcadams wrote: >> I have been irked for years that modem vendors haven't included TDD >> functionality in modems...it should be trivial to do. I had done >> some research into TDD's in the past and if I remember correctly, the >> "protocol" (such as it is) uses something like a 5N1 (5 data bits, no >> parity 1 stop bit) at some absurdly low baud rate (75 baud comes to >> mind, but I don't remember for sure). >Would that be V.18 you're thinking off? (ITU Text Telephone standard). Having done more research after my message last night....yes, V.18, as I understand it, basically encompasses interoperability with TDD type equipment basically all over the world. >ITU have a study group looking at how that extends to modern standards >incl. voice-over-IP etc., so someone must be interested in it. Indeed...it sounds like there is some interest in any case. >> I haven't seen any mentions on the list of anything like >> this...although I must admit to not following it too closely. >Is there an archive? There was a discussion about V.18 about a year >ago. Yeah...there is...mea culpa...I didn't see it last night when I was looking...I will say that it's not the most easily navigable archive I've ever seen. ;) I guess I should avoid doing research while under the influence of Benadryl. :/ >> Is there anyone doing work on this at this point? Anyone interested? >> I'm not sure how much help I could be, but I'd be glad to help out >> however I could. >Check the list and linmodems.org from time to time, so that when there >is progress on the main modem functionality, you can remind us about >TDD and volunteer to help. At the moment, no free software modem is >advanced enough to bother adding V.18 and the other standards, but that >will change. Understood...What is the status of handling of software modem equipment in general? My understanding is that there are drivers to treat the LT modems as sound cards at this point that are functional. That should be enough to, in the meantime, if I find someone interested that has more coding capability than a turnip (which is about my level) could code something up to work as a standalone piece of software. FWIW, for US anyway, traditional TDD's use 45.45 baud, 5 data bits, no parity, one and a half stop bits (weird, I know), 1400Hz and 1800Hz FSK, I'm assuming, but haven't found any information to support for sure, that the 1800Hz is a 1, and 1400Hz is a 0 in the transmission. It is carrier-less (basically transmitting in the blind), half-duplex (since there's only two frequencies) and has no negotiation. A description of the Baudot character codes used can be found at: http://telecom.tbi.net/baudot.html Anyway...I suspect that's probably actually enough information to implement this...so its in the record of the archives anyway. Any possibility that someone could add the possibility of using a software modem to do TDD capabilities as well to the linmodems.org site? "Think telephone emulation Think telephone with a backspace key ... Think Telecommunications Device for the Deaf (TDD/TTY)"? Oh...another tid-bit I picked up last night...apparently, most newer TDDs (as far as standalone equipment) also has support for Bell-103 300 baud ascii communication. There is still a huge installed base of older traditional Baudot-only equipment though. So, with newer TDD equipment, pretty much any computer modem with any comm software can interoperate using Bell-103. There's also software available in Windows for "Voice-modems" (basically any modems that expose the DSP functionality to the application as I understand it) that can use the "voice" capabilities to do the TDD "protocol." So...there's some information, so its in the archives, FWIW. Most of this information, I would assume, is included in the V.18 recommendation, and probably more as the V.18 recommendation is inclusive of many of the international standards as well (50 baud rather than 45.45 baud is common from what I understand). Thanks for the feedback...at least I have some idea of where things stand. :) -- Jeff McAdams Email: jeffm@iglou.com Head Network Administrator Voice: (502) 966-3848 IgLou Internet Services (800) 436-4456