Path: utzoo!news-server.csri.toronto.edu!rutgers!att!emory!swrinde!zaphod.mps.ohio-state.edu!think.com!mintaka!telecom-request From: hayes!tnixon@uunet.uu.net (Toby Nixon) Newsgroups: comp.dcom.telecom Subject: Re: V.32bis and V.17 adopted by CCITT Message-ID: Date: 11 Mar 91 10:06:19 GMT Sender: Telecom@eecs.nwu.edu Organization: Hayes Microcomputer Products, Norcross, GA Lines: 27 Approved: Telecom@eecs.nwu.edu X-Submissions-To: telecom@eecs.nwu.edu X-Administrivia-To: telecom-request@eecs.nwu.edu X-Telecom-Digest: Volume 11, Issue 198, Message 6 of 9 In article , peter@taronga.hackercorp. com (Peter da Silva) writes: >> V.17 is the new modulation scheme that provides 12000 and 14400 bps >> trellis-coded modulation for Group 3 facsimile. > Any relation to Telebit's proprietary "PEP" protocol? We should probably move this to comp.dcom.modems, but anyway... No, V.17 is not related to PEP at all. In fact, V.17 is _really_ a half-duplex version of V.32bis. The modulation scheme (constellation, coding, etc.) of V.17 is identical to V.32bis at 7200, 9600, 12000, and 14400. But because it is an application-specific modulation standard intended specifically for Group 3 fax, it is half-duplex. It includes a fast turnaround capability, talker echo protection, and "turn off" sequence, which apply to half-duplex modems only. V.17 also does NOT include the "rate signalling" bits of V.32bis, but instead depends on Group 3 negotiation procedures (T.30) to indicate data rate. 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