tnixon@hayes.uucp (03/08/91)
I received notice this morning via AT&T Mail from Dick Brandt, vice chairman of CCITT Study Group XVII, that V.17 and V.32bis were approved and are now formally adopted as CCITT Recommendations. He did not report the actually vote tally, but I assume that it was unanimous. V.17 is the new modulation scheme that provides 12000 and 14400 bps trellis-coded modulation for Group 3 facsimile. CCITT Recommendations T.4 and T.30, which define Group 3 fax, have also been amended to reference V.17 and provide for negotiation of its use (and those amendments have been adopted as well). V.17 also adds trellis-coded modulation at 7200 and 9600; these speeds are also provided in Group 3 fax by V.29 modulation but without trellis coding. V.17 should thus allow these speeds to be used on somewhat worse lines than was previously possible. V.32bis is an extension of CCITT V.32 which adds speeds of 7200, 12000, and 14400bps, full-duplex on two-wire dial-up or leased lines. V.32bis also adds a "rapid rate renegotiation" feature which allows the modems, by mutual agreement, to shift data rates up or down through a simple signalling process that takes about 1/10th of a second; V.32 requires a full retrain, which takes from 5 to 10 seconds, in order to change speeds. -- Toby Nixon, Principal Engineer | Voice +1-404-840-9200 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