Ron.Rothenberg@f460.n101.z1.fidonet.org (Ron Rothenberg) (01/05/90)
Index Number: 6054 Hi Jack, Here's some of the info on the IMS modem. I don't know if it's any good. This info is from the TDI International Telephone Directory. The fellow whose messages I posted is working on TSR software that will pop up in the middle of whatever you're doing and tell you you have a call. IMS Advanced 2445 Modem: TDD-TTY Compatibility: US/International Speeds. Automatic Baudot/ASCII detection Automatic Baudot/ASCII translation Auto Dial/Auto Answer Direct Connect PC Compatibility: Standard Personal Computeres MS-DOS 2.1 or higher. Fits standards 1/2 card 8-bit slot Small enough for portable computers ASCII Comunicationss 300 bps (Bell 103J) 1200 BPS (Bell 212A,CCiTT V.21) 2400 BPS! (CCITT V.22 bis) Hayes 2400 & 1200 Optional MNPS comperssion for 9600 bps Effective file transfer Improved Call Progress Status Software: (included with purchase) Memory Resident Visible Ring Signal One-key answer Compatible with commercial software For more info, please write to: Integrated Microcomputer Systems, Inc. 2 Research Place Rockville, MD 20850 -rsr- ... Always forgive your enemies - nothing annoys them so much. - O. Wilde -- Uucp: ..!{decvax,oliveb}!bunker!hcap!hnews!101!460!Ron.Rothenberg Internet: Ron.Rothenberg@f460.n101.z1.fidonet.org
Stephen.White@f853.n681.z3.fidonet.org (Stephen White) (01/05/90)
Index Number: 6092 OK - I still have the same question as I had a number of months ago. But now I know more - so perhaps I can ask the right question so you know what I want! With the International Speeds on TTD's (sic!) what is the CCITT spec number? (for all the speeds) And with the US standard, where could I get the technical data, like db levels for detect, etc etc... Just knowing the frequencies is not enough. And then, that damn terminal I'm getting built for me, and then programming myself can be finished! And some of you lucky people out there might get a demo model to play with, so I know how it compares against the wunnerful US of A homebrews! Steve! The Child of a Lesser God! -- Uucp: ..!{decvax,oliveb}!bunker!hcap!hnews!3!681!853!Stephen.White Internet: Stephen.White@f853.n681.z3.fidonet.org
rbarth@tumtum.cs.umd.edu (Richard Barth) (01/15/90)
Index Number: 6234 In Digest #1025 Stephen White writes: >With the International Speeds on TTD's (sic!) what is the CCITT spec <number? (for all the speeds) >And with the US standard, where could I get the technical data, like >db levels for detect, etc etc... Just knowing the frequencies is not >enough. I wouldn't look too hard for a CCITT standard; finding it wouldn't help. TDDs use the Baudot code. The standard rate for domestic (U.S.) TDDs is 45.45 baud, which is the "60 words per minute" used on teleprinters back in the days when everybody used Baudot machines. In Europe and elsewhere, 50 baud is commonly used. 50 baud. Baudot is termed a "7.42 unit code", because there are one start bit, five data bits, and 1.42 stop bits. Granted 1.42 stop bits sounds a bit strange, but it derives from the design of the old mechanical printers. Today, electronic componentry is used and 1.5 stop bits is commonly used, being available from UARTs such as the 8250 used in the IBM-PC and many clones. There are several kinds of "Baudot" code. The one described in the CCITT standard (if there is one) is unlikely to describe the way TDDs are actually built. Find yourself a copy of the ITT handbook (formal title is the "Radio Engineer's Handbook" at a library. It will probably (my old copy does) list four or five versions of "Baudot". One is the "International" (European) standard; one is the weather standard used by meteorologists and contains wind-direction symbols and the like; there's another whose specialty I forget. There is finally one termed the "U.S. Military standard". That's the one you want. It's also the standard used by ham radio operators, and you can get it out of the ARRL Handbook (The Radio Amateur's Handbook, pubslished by the American Radio Relay League, Newington CT.) TDDs differ from this version primarily in ignoring the bell code (what's a deaf person gonna do with THAT?) and the substitution of a backspace for the Baudot null. The other characteristics of TDDs are, unfortunately, non-standard. The Electronic Industries Assn. (EIA) formed a special committee that labored mightily for several years to develop a TDD standard. Unfortunately some of the companies in the TDD business (who were participating in the committee) went out of the TDD business. Those remaining couldn't agree on technical details. A final draft of the committee report was distributed to participants, and the committee died. You can probably get a copy of that draft from the EIA. The staff person was Peter Bennett; The EIA Committee was TR-41. EIA's address is: Electronic Industries Assn. 2001 Eye Street NW Washington DC 20006 If EIA can't help you let me know; I've still got my copy of the draft around here someplace - God knows where - and with luck I might even be able to find it.